diff --git a/ts/quill/signal-clipboard/index.dom.ts b/ts/quill/signal-clipboard/index.dom.ts
index ed62a50c32..c1a56a791f 100644
--- a/ts/quill/signal-clipboard/index.dom.ts
+++ b/ts/quill/signal-clipboard/index.dom.ts
@@ -80,33 +80,41 @@ export class SignalClipboard {
     }
 
     const { ops } = this.quill.getContents(selection.index, selection.length);
-    // Only enable formatting on the pasted text if the entire selection has it enabled!
-    const formats =
-      selection.length === 0
-        ? this.quill.getFormat(selection.index)
-        : {
-            [QuillFormattingStyle.bold]: FormattingMenu.isStyleEnabledForOps(
-              ops,
-              QuillFormattingStyle.bold
-            ),
-            [QuillFormattingStyle.italic]: FormattingMenu.isStyleEnabledForOps(
-              ops,
-              QuillFormattingStyle.italic
-            ),
-            [QuillFormattingStyle.monospace]:
-              FormattingMenu.isStyleEnabledForOps(
-                ops,
-                QuillFormattingStyle.monospace
-              ),
-            [QuillFormattingStyle.spoiler]: FormattingMenu.isStyleEnabledForOps(
-              ops,
-              QuillFormattingStyle.spoiler
-            ),
-            [QuillFormattingStyle.strike]: FormattingMenu.isStyleEnabledForOps(
-              ops,
-              QuillFormattingStyle.strike
-            ),
-          };
+
+    // Check if we're selecting all content
+    const totalLength = this.quill.getLength();
+    const isSelectingAll = selection.length >= totalLength - 1;
+
+    let formats: Record<string, unknown>;
+    if (selection.length === 0) {
+      formats = this.quill.getFormat(selection.index);
+    } else if (isSelectingAll) {
+      // No formatting for select-all
+      formats = {};
+    } else {
+      formats = {
+        [QuillFormattingStyle.bold]: FormattingMenu.isStyleEnabledForOps(
+          ops,
+          QuillFormattingStyle.bold
+        ),
+        [QuillFormattingStyle.italic]: FormattingMenu.isStyleEnabledForOps(
+          ops,
+          QuillFormattingStyle.italic
+        ),
+        [QuillFormattingStyle.monospace]: FormattingMenu.isStyleEnabledForOps(
+          ops,
+          QuillFormattingStyle.monospace
+        ),
+        [QuillFormattingStyle.spoiler]: FormattingMenu.isStyleEnabledForOps(
+          ops,
+          QuillFormattingStyle.spoiler
+        ),
+        [QuillFormattingStyle.strike]: FormattingMenu.isStyleEnabledForOps(
+          ops,
+          QuillFormattingStyle.strike
+        ),
+      };
+    }
     const clipboardDelta = signal
       ? clipboard.convert({ html: signal }, formats)
       : new Delta(insertEmojiOps(clipboard.convert({ text }, formats).ops, {}));
diff --git a/ts/test-electron/quill/signal-clipboard_test.dom.ts b/ts/test-electron/quill/signal-clipboard_test.dom.ts
new file mode 100644
index 0000000000..a2ac1af3de
--- /dev/null
+++ b/ts/test-electron/quill/signal-clipboard_test.dom.ts
@@ -0,0 +1,190 @@
+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import { Delta } from '@signalapp/quill-cjs';
+import type Quill from '@signalapp/quill-cjs';
+
+import { SignalClipboard } from '../../quill/signal-clipboard/index.dom.js';
+import { QuillFormattingStyle } from '../../quill/formatting/menu.dom.js';
+
+class MockQuill {
+  public root: HTMLElement;
+  public clipboard: {
+    convert: (data: unknown, formats: Record<string, unknown>) => Delta;
+  };
+  public selection: {
+    getRange: () => Array<unknown> | [null];
+    update: (mode: string) => void;
+  };
+  public getContents: (
+    index: number,
+    length: number
+  ) => { ops: Array<unknown> };
+  public getSelection: () => { index: number; length: number } | null;
+  public getLength: () => number;
+  public getFormat: (index: number) => Record<string, unknown>;
+  public updateContents: (delta: Delta, source: string) => void;
+  public setSelection: (index: number, length: number, mode: string) => void;
+  public scrollSelectionIntoView: () => void;
+  public focus: () => void;
+
+  constructor() {
+    this.root = document.createElement('div');
+    this.clipboard = {
+      convert: (_data: unknown, formats: Record<string, unknown>) => {
+        // Mock clipboard conversion - returns delta
+        const text = 'test';
+        return new Delta([{ insert: text, attributes: formats }]);
+      },
+    };
+    this.selection = {
+      getRange: () => [null],
+      update: () => {
+        // Placeholder for linter
+      },
+    };
+    this.getContents = (_index: number, _length: number) => ({ ops: [] });
+    this.getSelection = () => ({ index: 0, length: 0 });
+    this.getLength = () => 1;
+    this.getFormat = () => ({});
+    this.updateContents = () => {
+      // Placeholder for linter
+    };
+    this.setSelection = () => {
+      // Placeholder for linter
+    };
+    this.scrollSelectionIntoView = () => {
+      // Placeholder for linter
+    };
+    this.focus = () => {
+      // Placeholder for linter
+    };
+  }
+}
+
+function createMockClipboardEvent(
+  textData: string | null = null,
+  signalData: string | null = null
+): ClipboardEvent {
+  const event = new Event('paste') as ClipboardEvent;
+  Object.defineProperty(event, 'clipboardData', {
+    value: {
+      getData: (format: string) => {
+        if (format === 'text/plain') {
+          return textData || '';
+        }
+        if (format === 'text/signal') {
+          return signalData || '';
+        }
+        return '';
+      },
+      files: null,
+    } as unknown as DataTransfer,
+    writable: false,
+  });
+  return event;
+}
+
+function createMockQuillWithContent(
+  content: string,
+  hasStrike: boolean = false
+): MockQuill {
+  const mockQuill = new MockQuill();
+
+  mockQuill.getContents = () => ({
+    ops: [
+      {
+        insert: content,
+        attributes: hasStrike ? { [QuillFormattingStyle.strike]: true } : {},
+      },
+    ],
+  });
+
+  mockQuill.getLength = () => content.length + 1;
+
+  return mockQuill;
+}
+
+describe('SignalClipboard', () => {
+  let mockQuill: MockQuill;
+  let clipboard: SignalClipboard;
+
+  beforeEach(() => {
+    mockQuill = new MockQuill();
+    clipboard = new SignalClipboard(mockQuill as unknown as Quill, {
+      isDisabled: false,
+    });
+  });
+
+  describe('onCapturePaste', () => {
+    describe('when pasting plain text', () => {
+      it('should not inherit strikethrough formatting from selected text', () => {
+        const content = 'Hello world';
+        mockQuill = createMockQuillWithContent(content, true);
+        clipboard = new SignalClipboard(mockQuill as unknown as Quill, {
+          isDisabled: false,
+        });
+
+        // Select all
+        mockQuill.getSelection = () => ({ index: 0, length: content.length });
+
+        // Conversion to delta
+        let capturedFormats: Record<string, unknown> | null = null;
+        mockQuill.clipboard.convert = (
+          _data: unknown,
+          formats: Record<string, unknown>
+        ) => {
+          capturedFormats = formats;
+          return new Delta([{ insert: 'test', attributes: formats }]);
+        };
+
+        // Paste
+        const pasteEvent = createMockClipboardEvent('New text', null);
+        clipboard.onCapturePaste(pasteEvent);
+
+        // Assert no formatting
+        assert.deepEqual(capturedFormats, {});
+      });
+
+      it('should not inherit any formatting from selected text', () => {
+        const content = 'Hello world';
+        mockQuill = createMockQuillWithContent(content, false);
+        mockQuill.getContents = () => ({
+          ops: [
+            {
+              insert: content,
+              attributes: {
+                [QuillFormattingStyle.bold]: true,
+                [QuillFormattingStyle.italic]: true,
+              },
+            },
+          ],
+        });
+        clipboard = new SignalClipboard(mockQuill as unknown as Quill, {
+          isDisabled: false,
+        });
+
+        // Select all content
+        mockQuill.getSelection = () => ({ index: 0, length: content.length });
+
+        // Conversion to delta
+        let capturedFormats: Record<string, unknown> | null = null;
+        mockQuill.clipboard.convert = (
+          _data: unknown,
+          formats: Record<string, unknown>
+        ) => {
+          capturedFormats = formats;
+          return new Delta([{ insert: 'test', attributes: formats }]);
+        };
+
+        // Paste
+        const pasteEvent = createMockClipboardEvent('New text', null);
+        clipboard.onCapturePaste(pasteEvent);
+
+        // Assert no formatting
+        assert.deepEqual(capturedFormats, {});
+      });
+    });
+  });
+});