diff --git a/frontend/src/lib/components/CommentMessage.svelte b/frontend/src/lib/components/CommentMessage.svelte
new file mode 100644
index 00000000..f32e7d7d
--- /dev/null
+++ b/frontend/src/lib/components/CommentMessage.svelte
@@ -0,0 +1,111 @@
+<script lang="ts">
+import { m } from '$lib/paraglide/messages.js';
+import type { FlatMessage } from '$lib/types';
+import { extractQuote } from '$lib/utils/comment';
+import { getInitials } from '$lib/utils/personFormat';
+import { relativeTime } from '$lib/utils/time';
+import { renderBody } from '$lib/utils/mention';
+
+type Props = {
+	message: FlatMessage;
+	isOwn: boolean;
+	isEditing: boolean;
+	editText: string;
+	onEdit: () => void;
+	onDelete: () => void;
+	onEditTextChange: (text: string) => void;
+	onEditKeydown: (e: KeyboardEvent) => void;
+};
+
+let {
+	message,
+	isOwn,
+	isEditing,
+	editText,
+	onEdit,
+	onDelete,
+	onEditTextChange,
+	onEditKeydown
+}: Props = $props();
+
+const wasEdited = $derived(message.updatedAt > message.createdAt);
+const parsed = $derived(extractQuote(message.content));
+</script>
+
+<div role="article" class="flex gap-2">
+	<!-- Avatar circle with initials -->
+	<div
+		class="flex h-6 w-6 shrink-0 items-center justify-center rounded-full bg-primary text-[10px] font-bold text-primary-fg"
+	>
+		{getInitials(message.authorName)}
+	</div>
+
+	<!-- Content -->
+	<div class="min-w-0 flex-1">
+		<!-- Author + timestamp -->
+		<div class="flex items-center gap-1.5">
+			<span class="font-sans text-sm font-semibold text-ink">{message.authorName}</span>
+			{#if wasEdited}
+				<span class="font-sans text-xs text-ink-3"
+					>{relativeTime(message.updatedAt)} {m.comment_edited_label()}</span
+				>
+			{:else}
+				<span class="font-sans text-xs text-ink-3">{relativeTime(message.createdAt)}</span>
+			{/if}
+		</div>
+
+		<!-- Quote block (if present) -->
+		{#if parsed.quote}
+			<div class="my-1 border-l-2 border-line pl-2 font-serif text-base text-ink-3 italic">
+				&ldquo;{parsed.quote}&rdquo;
+			</div>
+		{/if}
+
+		<!-- Edit mode vs view mode -->
+		{#if isEditing}
+			<textarea
+				class="mt-1 w-full resize-none rounded border border-line bg-surface px-2 py-1 font-serif text-sm leading-relaxed text-ink outline-none focus:border-primary"
+				rows={2}
+				value={editText}
+				oninput={(e) => onEditTextChange((e.currentTarget as HTMLTextAreaElement).value)}
+				onkeydown={onEditKeydown}
+			></textarea>
+			<div class="mt-1 font-sans text-xs text-ink-3">Enter speichern · Esc abbrechen</div>
+		{:else}
+			<!-- svelte-ignore a11y_click_events_have_key_events -->
+			<!-- svelte-ignore a11y_no_static_element_interactions -->
+			<div class="relative" onclick={() => { if (isOwn) onEdit(); }}>
+				<p
+					class="font-serif text-base leading-relaxed text-ink-2 {isOwn
+						? '-mx-1 cursor-text rounded px-1 transition-colors hover:bg-surface'
+						: ''}"
+				>
+					<!-- eslint-disable-next-line svelte/no-at-html-tags -- renderBody escapes all HTML before injecting mention links -->
+					{@html renderBody(parsed.body, message.mentionDTOs ?? [])}
+				</p>
+				{#if isOwn}
+					<button
+						type="button"
+						class="hover:text-error absolute -right-1 -bottom-1 cursor-pointer rounded p-2 text-ink-3 transition-colors"
+						aria-label="{m.btn_delete()} {message.authorName}"
+						onclick={(e) => { e.stopPropagation(); onDelete(); }}
+					>
+						<svg
+							class="h-4 w-4"
+							fill="none"
+							viewBox="0 0 24 24"
+							stroke="currentColor"
+							stroke-width="1.5"
+						>
+							<path
+								stroke-linecap="round"
+								stroke-linejoin="round"
+								d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16"
+							/>
+						</svg>
+					</button>
+				{/if}
+			</div>
+		{/if}
+	</div>
+</div>
diff --git a/frontend/src/lib/components/CommentMessage.svelte.spec.ts b/frontend/src/lib/components/CommentMessage.svelte.spec.ts
new file mode 100644
index 00000000..9c1f7d75
--- /dev/null
+++ b/frontend/src/lib/components/CommentMessage.svelte.spec.ts
@@ -0,0 +1,85 @@
+import { describe, it, expect, vi, afterEach } from 'vitest';
+import { cleanup, render } from 'vitest-browser-svelte';
+import { page, userEvent } from 'vitest/browser';
+import CommentMessage from './CommentMessage.svelte';
+import type { FlatMessage } from '$lib/types';
+
+afterEach(cleanup);
+
+const baseMsg: FlatMessage = {
+	id: 'msg-1',
+	authorId: 'user-1',
+	authorName: 'Anna Müller',
+	content: 'Hello world',
+	createdAt: new Date(Date.now() - 5 * 60_000).toISOString(),
+	updatedAt: new Date(Date.now() - 5 * 60_000).toISOString()
+};
+
+function defaultProps(overrides: Partial<Parameters<typeof render>[1]> = {}) {
+	return {
+		message: baseMsg,
+		isOwn: false,
+		isEditing: false,
+		editText: '',
+		onEdit: vi.fn(),
+		onDelete: vi.fn(),
+		onEditTextChange: vi.fn(),
+		onEditKeydown: vi.fn(),
+		...overrides
+	};
+}
+
+describe('CommentMessage', () => {
+	it('renders author name', async () => {
+		render(CommentMessage, defaultProps());
+		await expect.element(page.getByText('Anna Müller')).toBeInTheDocument();
+	});
+
+	it('renders initials in avatar', async () => {
+		render(CommentMessage, defaultProps());
+		await expect.element(page.getByText('AM')).toBeInTheDocument();
+	});
+
+	it('renders message body', async () => {
+		render(CommentMessage, defaultProps());
+		await expect.element(page.getByText('Hello world')).toBeInTheDocument();
+	});
+
+	it('renders quoted section when content contains a quote', async () => {
+		render(
+			CommentMessage,
+			defaultProps({
+				message: { ...baseMsg, content: '> "Interesting passage"\n\nMy reply' }
+			})
+		);
+		await expect.element(page.getByText(/Interesting passage/)).toBeInTheDocument();
+		await expect.element(page.getByText('My reply')).toBeInTheDocument();
+	});
+
+	it('does not show delete button for messages not owned by current user', async () => {
+		render(CommentMessage, defaultProps({ isOwn: false }));
+		await expect.element(page.getByRole('button')).not.toBeInTheDocument();
+	});
+
+	it('shows delete button for own messages', async () => {
+		render(CommentMessage, defaultProps({ isOwn: true }));
+		await expect.element(page.getByRole('button')).toBeInTheDocument();
+	});
+
+	it('calls onDelete when delete button is clicked', async () => {
+		const onDelete = vi.fn();
+		render(CommentMessage, defaultProps({ isOwn: true, onDelete }));
+		await userEvent.click(page.getByRole('button'));
+		expect(onDelete).toHaveBeenCalled();
+	});
+
+	it('shows edit textarea when isEditing is true', async () => {
+		render(
+			CommentMessage,
+			defaultProps({ isOwn: true, isEditing: true, editText: 'current edit text' })
+		);
+		const textarea = page.getByRole('textbox');
+		await expect.element(textarea).toBeInTheDocument();
+		await expect.element(textarea).toHaveValue('current edit text');
+	});
+});
diff --git a/frontend/src/lib/components/CommentThread.svelte b/frontend/src/lib/components/CommentThread.svelte
index 1d5ce5e5..f943c671 100644
--- a/frontend/src/lib/components/CommentThread.svelte
+++ b/frontend/src/lib/components/CommentThread.svelte
@@ -1,13 +1,10 @@
 <script lang="ts">
 import { onMount, untrack } from 'svelte';
 import { m } from '$lib/paraglide/messages.js';
-import type { Comment } from '$lib/types';
+import type { Comment, FlatMessage } from '$lib/types';
 import MentionEditor from '$lib/components/MentionEditor.svelte';
-import { renderBody, extractContent } from '$lib/utils/mention';
-import { relativeTime } from '$lib/utils/time';
-import { getInitials } from '$lib/utils/personFormat';
-import type { MentionDTO } from '$lib/types';
-
+import CommentMessage from '$lib/components/CommentMessage.svelte';
+import { extractContent } from '$lib/utils/mention';
 type Props = {
 	documentId: string;
 	annotationId?: string | null;
@@ -34,16 +31,6 @@ let {
 	onCountChange
 }: Props = $props();
 
-type FlatMessage = {
-	id: string;
-	authorId: string | null;
-	authorName: string;
-	content: string;
-	createdAt: string;
-	updatedAt: string;
-	mentionDTOs?: MentionDTO[];
-};
-
 let comments: Comment[] = $state(untrack(() => [...initialComments]));
 let newText: string = $state('');
 let posting: boolean = $state(false);
@@ -69,20 +56,10 @@ $effect(() => {
 	}
 });
 
-function wasEdited(c: { createdAt: string; updatedAt: string }): boolean {
-	return c.updatedAt > c.createdAt;
-}
-
 function isOwn(c: { authorId: string | null }): boolean {
 	return currentUserId !== null && c.authorId === currentUserId;
 }
 
-function extractQuote(content: string): { quote: string | null; body: string } {
-	const match = content.match(/^>\s*"(.+?)"\s*\n\n?([\s\S]*)$/);
-	if (match) return { quote: match[1], body: match[2] };
-	return { quote: null, body: content };
-}
-
 async function reload() {
 	try {
 		const res = await fetch(commentsBase);
@@ -204,77 +181,18 @@ onMount(() => {
 			{flatMessages.length === 1 ? 'Kommentar' : 'Kommentare'}
 		</div>
 
-		<div class="space-y-2">
+		<div role="log" class="space-y-2">
 			{#each flatMessages as msg (msg.id)}
-				{@const parsed = extractQuote(msg.content)}
-				<div class="flex gap-2">
-					<div
-						class="flex h-6 w-6 shrink-0 items-center justify-center rounded-full bg-primary text-[10px] font-bold text-primary-fg"
-					>
-						{getInitials(msg.authorName)}
-					</div>
-					<div class="min-w-0 flex-1">
-						<div class="flex items-center gap-1.5">
-							<span class="font-sans text-sm font-semibold text-ink">{msg.authorName}</span>
-							{#if wasEdited(msg)}
-								<span class="font-sans text-xs text-ink-3"
-									>{relativeTime(msg.updatedAt)} {m.comment_edited_label()}</span
-								>
-							{:else}
-								<span class="font-sans text-xs text-ink-3">{relativeTime(msg.createdAt)}</span>
-							{/if}
-						</div>
-						{#if parsed.quote}
-							<div class="my-1 border-l-2 border-line pl-2 font-serif text-base text-ink-3 italic">
-								&ldquo;{parsed.quote}&rdquo;
-							</div>
-						{/if}
-
-						{#if editingId === msg.id}
-							<textarea
-								class="mt-1 w-full resize-none rounded border border-line bg-surface px-2 py-1 font-serif text-sm leading-relaxed text-ink outline-none focus:border-primary"
-								rows={2}
-								bind:value={editText}
-								onkeydown={(e) => handleEditKeydown(e, msg.id)}
-							></textarea>
-							<div class="mt-1 font-sans text-xs text-ink-3">Enter speichern · Esc abbrechen</div>
-						{:else}
-							<!-- svelte-ignore a11y_click_events_have_key_events -->
-							<!-- svelte-ignore a11y_no_static_element_interactions -->
-							<div class="relative" onclick={() => { if (isOwn(msg)) startEdit(msg); }}>
-								<p
-									class="font-serif text-base leading-relaxed text-ink-2 {isOwn(msg) ? '-mx-1 cursor-text rounded px-1 transition-colors hover:bg-surface' : ''}"
-								>
-									<!-- eslint-disable-next-line svelte/no-at-html-tags -- renderBody escapes all HTML before injecting mention links -->
-									{@html renderBody(parsed.body, msg.mentionDTOs ?? [])}
-								</p>
-								{#if isOwn(msg)}
-									<button
-										type="button"
-										class="hover:text-error absolute -right-1 -bottom-1 cursor-pointer rounded p-0.5 text-ink-3 transition-colors"
-										title={m.btn_delete()}
-										aria-label={m.btn_delete()}
-										onclick={(e) => { e.stopPropagation(); deleteComment(msg.id); }}
-									>
-										<svg
-											class="h-4 w-4"
-											fill="none"
-											viewBox="0 0 24 24"
-											stroke="currentColor"
-											stroke-width="1.5"
-										>
-											<path
-												stroke-linecap="round"
-												stroke-linejoin="round"
-												d="M19 7l-.867 12.142A2 2 0 0116.138 21H7.862a2 2 0 01-1.995-1.858L5 7m5 4v6m4-6v6m1-10V4a1 1 0 00-1-1h-4a1 1 0 00-1 1v3M4 7h16"
-											/>
-										</svg>
-									</button>
-								{/if}
-							</div>
-						{/if}
-					</div>
-				</div>
+				<CommentMessage
+					message={msg}
+					isOwn={isOwn(msg)}
+					isEditing={editingId === msg.id}
+					editText={editText}
+					onEdit={() => startEdit(msg)}
+					onDelete={() => deleteComment(msg.id)}
+					onEditTextChange={(text) => { editText = text; }}
+					onEditKeydown={(e) => handleEditKeydown(e, msg.id)}
+				/>
 			{/each}
 		</div>
 	</div>
diff --git a/frontend/src/lib/types.ts b/frontend/src/lib/types.ts
index 24dbb848..2458d35a 100644
--- a/frontend/src/lib/types.ts
+++ b/frontend/src/lib/types.ts
@@ -14,6 +14,16 @@ export type CommentReply = {
 	mentionDTOs?: MentionDTO[];
 };
 
+export type FlatMessage = {
+	id: string;
+	authorId: string | null;
+	authorName: string;
+	content: string;
+	createdAt: string;
+	updatedAt: string;
+	mentionDTOs?: MentionDTO[];
+};
+
 export type Comment = {
 	id: string;
 	authorId: string | null;
diff --git a/frontend/src/lib/utils/comment.spec.ts b/frontend/src/lib/utils/comment.spec.ts
new file mode 100644
index 00000000..74587929
--- /dev/null
+++ b/frontend/src/lib/utils/comment.spec.ts
@@ -0,0 +1,40 @@
+import { describe, it, expect } from 'vitest';
+import { extractQuote } from './comment';
+
+describe('extractQuote', () => {
+	it('returns null quote and full body for plain text', () => {
+		const result = extractQuote('Hello world');
+		expect(result.quote).toBeNull();
+		expect(result.body).toBe('Hello world');
+	});
+
+	it('extracts quote and body with double newline separator', () => {
+		const result = extractQuote('> "Some quoted text"\n\nReply body');
+		expect(result.quote).toBe('Some quoted text');
+		expect(result.body).toBe('Reply body');
+	});
+
+	it('extracts quote and body with single newline separator', () => {
+		const result = extractQuote('> "Quote"\nBody');
+		expect(result.quote).toBe('Quote');
+		expect(result.body).toBe('Body');
+	});
+
+	it('returns null quote when format does not match', () => {
+		const result = extractQuote('> Not a quote format');
+		expect(result.quote).toBeNull();
+		expect(result.body).toBe('> Not a quote format');
+	});
+
+	it('handles empty string', () => {
+		const result = extractQuote('');
+		expect(result.quote).toBeNull();
+		expect(result.body).toBe('');
+	});
+
+	it('does not match when quotes are missing', () => {
+		const result = extractQuote('> just a blockquote\n\nbody');
+		expect(result.quote).toBeNull();
+		expect(result.body).toBe('> just a blockquote\n\nbody');
+	});
+});
diff --git a/frontend/src/lib/utils/comment.ts b/frontend/src/lib/utils/comment.ts
new file mode 100644
index 00000000..ac99c5d5
--- /dev/null
+++ b/frontend/src/lib/utils/comment.ts
@@ -0,0 +1,5 @@
+export function extractQuote(content: string): { quote: string | null; body: string } {
+	const match = content.match(/^>\s*"(.+?)"\s*\n\n?([\s\S]*)$/);
+	if (match) return { quote: match[1], body: match[2] };
+	return { quote: null, body: content };
+}