diff --git a/lib/shared/message-utils.js b/lib/shared/message-utils.js
--- a/lib/shared/message-utils.js
+++ b/lib/shared/message-utils.js
@@ -31,6 +31,7 @@
 import type { RelativeUserInfo, UserInfos } from '../types/user-types';
 import { codeBlockRegex, type ParserRules } from './markdown';
 import { messageSpecs } from './messages/message-specs';
+import { threadIsGroupChat } from './thread-utils';
 import { stringForUser } from './user-utils';
 
 const localIDPrefix = 'local';
@@ -507,6 +508,35 @@
   };
 }
 
+type MessagePreviewResult = {
+  +message: string,
+  +username: ?string,
+};
+function getMessagePreview(
+  originalMessageInfo: MessageInfo,
+  threadInfo: ThreadInfo,
+  markdownRules: ParserRules,
+): MessagePreviewResult {
+  const messageInfo: ComposableMessageInfo | RobotextMessageInfo =
+    originalMessageInfo.type === messageTypes.SIDEBAR_SOURCE
+      ? originalMessageInfo.sourceMessage
+      : originalMessageInfo;
+
+  const messageTitle = getMessageTitle(messageInfo, threadInfo, markdownRules);
+
+  const hasUsername =
+    threadIsGroupChat(threadInfo) ||
+    threadInfo.name !== '' ||
+    messageInfo.creator.isViewer;
+
+  let userString = null;
+  if (messageInfo.type === messageTypes.TEXT && hasUsername) {
+    userString = stringForUser(messageInfo.creator);
+  }
+
+  return { message: messageTitle, username: userString };
+}
+
 export {
   localIDPrefix,
   messageKey,
@@ -534,4 +564,5 @@
   getMessageTitle,
   removeCreatorAsViewer,
   mergeThreadMessageInfos,
+  getMessagePreview,
 };
diff --git a/web/chat/message-preview.react.js b/web/chat/message-preview.react.js
--- a/web/chat/message-preview.react.js
+++ b/web/chat/message-preview.react.js
@@ -3,15 +3,8 @@
 import classNames from 'classnames';
 import * as React from 'react';
 
-import { getMessageTitle } from 'lib/shared/message-utils';
-import { threadIsGroupChat } from 'lib/shared/thread-utils';
-import { stringForUser } from 'lib/shared/user-utils';
-import {
-  type MessageInfo,
-  messageTypes,
-  type ComposableMessageInfo,
-  type RobotextMessageInfo,
-} from 'lib/types/message-types';
+import { getMessagePreview } from 'lib/shared/message-utils';
+import { type MessageInfo } from 'lib/types/message-types';
 import { type ThreadInfo } from 'lib/types/thread-types';
 
 import { getDefaultTextMessageRules } from '../markdown/rules.react';
@@ -38,26 +31,16 @@
       </div>
     );
   }
-  const messageInfo: ComposableMessageInfo | RobotextMessageInfo =
-    originalMessageInfo.type === messageTypes.SIDEBAR_SOURCE
-      ? originalMessageInfo.sourceMessage
-      : originalMessageInfo;
 
-  const messageTitle = getMessageTitle(
-    messageInfo,
+  const { message: messageTitle, username } = getMessagePreview(
+    originalMessageInfo,
     threadInfo,
     getDefaultTextMessageRules().simpleMarkdownRules,
   );
 
-  const hasUsername =
-    threadIsGroupChat(threadInfo) ||
-    threadInfo.name !== '' ||
-    messageInfo.creator.isViewer;
-
   let usernameText = null;
-  if (messageInfo.type === messageTypes.TEXT && hasUsername) {
-    const userString = stringForUser(messageInfo.creator);
-    usernameText = <span className={colorStyle}>{`${userString}: `}</span>;
+  if (username) {
+    usernameText = <span className={colorStyle}>{`${username}: `}</span>;
   }
 
   return (