diff --git a/src/models/Message.js b/src/models/Message.js
index baebd14..7aae392 100644
--- a/src/models/Message.js
+++ b/src/models/Message.js
@@ -54,6 +54,11 @@
     return this.data[1]?.[37] ?? null;
   }
 
+  clearParentMessageId() {
+    if (!this.data[1]) return;
+    delete this.data[1][37];
+  }
+
   isComment() {
     return !!this.getParentMessageId;
   }
diff --git a/src/xhrInterceptor/responseModifiers/createMessageRemoveParentRef.js b/src/xhrInterceptor/responseModifiers/createMessageRemoveParentRef.js
new file mode 100644
index 0000000..a127975
--- /dev/null
+++ b/src/xhrInterceptor/responseModifiers/createMessageRemoveParentRef.js
@@ -0,0 +1,16 @@
+const createMessageRemoveParentRef = {
+  urlRegex: /api\/CreateMessage/i,
+  featureGated: true,
+  features: ['flattenthreads', 'flattenthreads_switch_enabled'],
+  isEnabled(options) {
+    return options['flattenthreads'] &&
+        options['flattenthreads_switch_enabled'];
+  },
+  async interceptor(_request, response) {
+    // Remove parent_message_id value (field 37)
+    delete response[37];
+    return response;
+  }
+};
+
+export default createMessageRemoveParentRef;
diff --git a/src/xhrInterceptor/responseModifiers/flattenThread.js b/src/xhrInterceptor/responseModifiers/flattenThread.js
index 23db6eb..53828eb 100644
--- a/src/xhrInterceptor/responseModifiers/flattenThread.js
+++ b/src/xhrInterceptor/responseModifiers/flattenThread.js
@@ -2,7 +2,7 @@
 import GapModel from '../../models/Gap.js';
 import MessageModel from '../../models/Message.js';
 
-const loadMoreThread = {
+const flattenThread = {
   urlRegex: /api\/ViewThread/i,
   featureGated: true,
   features: ['flattenthreads', 'flattenthreads_switch_enabled'],
@@ -42,6 +42,9 @@
     });
     mogs.forEach(m => m.setPayload(m.newPayload));
 
+    // Clear parent_message_id fields
+    mogs.forEach(m => m.clearParentMessageId());
+
     // Sort the messages by date
     mogs.sort((a, b) => {
       const c = a instanceof MessageModel ? a.getCreatedMicroseconds() :
@@ -54,6 +57,10 @@
 
     response[1][40] = mogs.map(mog => mog.toRawMessageOrGap());
 
+    // Set last_message to the last message after sorting
+    if (response[1]?.[17]?.[3])
+      response[1][17][3] = response[1][40].slice(-1)?.[1];
+
     // Set num_messages to the updated value, since we've flattened the replies.
     response[1][8] = response[1][40].length;
     return response;
@@ -76,8 +83,7 @@
     else
       prevId = parentId;
 
-    const prevMessage =
-        prevId ? mogs.find(m => m.getId() == prevId) : null;
+    const prevMessage = prevId ? mogs.find(m => m.getId() == prevId) : null;
 
     return {
       isComment: true,
@@ -93,4 +99,4 @@
   }
 };
 
-export default loadMoreThread;
+export default flattenThread;
diff --git a/src/xhrInterceptor/responseModifiers/index.js b/src/xhrInterceptor/responseModifiers/index.js
index 43ffe6c..40494eb 100644
--- a/src/xhrInterceptor/responseModifiers/index.js
+++ b/src/xhrInterceptor/responseModifiers/index.js
@@ -3,10 +3,12 @@
 
 import loadMoreThread from './loadMoreThread.js';
 import flattenThread from './flattenThread.js';
+import createMessageRemoveParentRef from './createMessageRemoveParentRef.js';
 
 export const responseModifiers = [
   loadMoreThread,
   flattenThread,
+  createMessageRemoveParentRef,
 ];
 
 // Content script target