diff --git a/src/xhrInterceptor/responseModifiers/flattenThread.js b/src/xhrInterceptor/responseModifiers/flattenThread.js
index 65eb42c..cece8b4 100644
--- a/src/xhrInterceptor/responseModifiers/flattenThread.js
+++ b/src/xhrInterceptor/responseModifiers/flattenThread.js
@@ -1,3 +1,4 @@
+import {kAdditionalInfoPrefix} from '../../contentScripts/communityConsole/flattenThreads/flattenThreads.js';
 import GapModel from '../../models/Gap.js';
 import MessageModel from '../../models/Message.js';
 
@@ -12,6 +13,7 @@
   async interceptor(_request, response) {
     if (!response[1]?.[40]) return response;
 
+    // Do the actual flattening
     const originalMogs =
         MessageModel.mapToMessageOrGapModels(response[1][40] ?? []);
     let extraMogs = [];
@@ -22,6 +24,19 @@
       mog.clearCommentsAndGaps();
     });
     const mogs = originalMogs.concat(extraMogs);
+
+    // Add some message data to the payload so the extension can show the parent
+    // comment/reply in the case of comments.
+    mogs.forEach(m => {
+      const info = this.getAdditionalInformation(m, mogs);
+      const span = document.createElement('span');
+      span.textContent = kAdditionalInfoPrefix + JSON.stringify(info);
+      span.setAttribute('style', 'display: none');
+      m.newPayload = m.getPayload() + span.outerHTML;
+    });
+    mogs.forEach(m => m.setPayload(m.newPayload));
+
+    // Sort the messages by date
     mogs.sort((a, b) => {
       const c = a instanceof MessageModel ? a.getCreatedMicroseconds() :
                                             a.getStartTimestamp();
@@ -30,11 +45,35 @@
       const diff = c - d;
       return diff > 0 ? 1 : diff < 0 ? -1 : 0;
     });
+
     response[1][40] = mogs.map(mog => mog.toRawMessageOrGap());
+
     // Set num_messages to the updated value, since we've flattened the replies.
     response[1][8] = response[1][40].length;
     return response;
   },
+  getAdditionalInformation(message, mogs) {
+    const id = message.getId();
+    const parentId = message.getParentMessageId();
+    const parentMessage =
+        parentId ? mogs.find(m => m.getId() === parentId) : null;
+    if (!parentMessage) {
+      return {
+        isComment: false,
+        id,
+      };
+    }
+
+    return {
+      isComment: true,
+      id,
+      parentMessage: {
+        id: parentId,
+        payload: parentMessage.getPayload(),
+        author: parentMessage.getAuthor(),
+      },
+    };
+  }
 };
 
 export default loadMoreThread;