diff --git a/src/contentScripts/communityConsole/flattenThreads/flattenThreads.js b/src/contentScripts/communityConsole/flattenThreads/flattenThreads.js
new file mode 100644
index 0000000..91bcfbb
--- /dev/null
+++ b/src/contentScripts/communityConsole/flattenThreads/flattenThreads.js
@@ -0,0 +1,55 @@
+export const kAdditionalInfoPrefix = '__TWPT_FLATTENTHREADS_ADDITIONALINFO__';
+export const kAdditionalInfoRegex =
+    /^__TWPT_FLATTENTHREADS_ADDITIONALINFO__(.*)/;
+
+export const kReplyPayloadSelector =
+    '.scTailwindThreadMessageMessagecardcontent:not(.scTailwindThreadMessageMessagecardpromoted) .scTailwindThreadPostcontentroot html-blob';
+
+export default class FlattenThreads {
+  construct() {}
+
+  getExtraInfo(node) {
+    let rawExtraInfo = null;
+    const possibleExtraInfoNodes =
+        node.querySelectorAll('span[style*=\'display\'][style*=\'none\']');
+    for (const candidate of possibleExtraInfoNodes) {
+      const content = candidate.textContent;
+      const matches = content.match(kAdditionalInfoRegex);
+      if (matches) {
+        rawExtraInfo = matches?.[1] ?? null;
+        break;
+      }
+    }
+    if (!rawExtraInfo) return null;
+    return JSON.parse(rawExtraInfo);
+  }
+
+  injectId(node, extraInfo) {
+    const root = node.closest('.scTailwindThreadMessageMessagecardcontent');
+    if (!root) return false;
+    root.setAttribute('data-twpt-message-id', extraInfo.id);
+    return true;
+  }
+
+  injectQuote(node, extraInfo) {
+    const content = node.closest('.scTailwindThreadPostcontentroot');
+    // @TODO: Change this by the actual quote component
+    const quote = document.createElement('div');
+    quote.textContent = 'QUOTE(' + extraInfo.parentMessage.id + ')';
+    content.prepend(quote);
+  }
+
+  injectIfApplicable(node) {
+    // If we injected the additional information, it means the flatten threads
+    // feature is enabled and in actual use, so we should inject the quote.
+    const extraInfo = this.getExtraInfo(node);
+    if (!extraInfo) return;
+
+    this.injectId(node, extraInfo);
+    if (extraInfo.isComment) this.injectQuote(node, extraInfo);
+  }
+
+  shouldInject(node) {
+    return node.matches(kReplyPayloadSelector);
+  }
+}
diff --git a/src/contentScripts/communityConsole/main.js b/src/contentScripts/communityConsole/main.js
index 1edb466..a3b1bb7 100644
--- a/src/contentScripts/communityConsole/main.js
+++ b/src/contentScripts/communityConsole/main.js
@@ -8,6 +8,7 @@
 // #!if ['chromium', 'chromium_mv3'].includes(browser_target)
 import {applyDragAndDropFixIfEnabled} from './dragAndDropFix.js';
 // #!endif
+import {default as FlattenThreads, kReplyPayloadSelector} from './flattenThreads/flattenThreads.js';
 import InfiniteScroll from './infiniteScroll.js';
 import {kRepliesSectionSelector} from './threadToolbar/constants.js';
 import ThreadToolbar from './threadToolbar/threadToolbar.js';
@@ -15,7 +16,7 @@
 import Workflows from './workflows/workflows.js';
 
 var mutationObserver, options, avatars, infiniteScroll, workflows,
-    threadToolbar;
+    threadToolbar, flattenThreads;
 
 const watchedNodesSelectors = [
   // App container (used to set up the intersection observer and inject the dark
@@ -76,6 +77,9 @@
 
   // Thread page reply section (for the thread page toolbar)
   kRepliesSectionSelector,
+
+  // Reply payload (for the flatten threads UI)
+  kReplyPayloadSelector,
 ];
 
 function handleCandidateNode(node) {
@@ -214,6 +218,11 @@
     if (threadToolbar.shouldInject(node)) {
       threadToolbar.injectIfApplicable(node);
     }
+
+    // Inject parent reply quote
+    if (flattenThreads.shouldInject(node)) {
+      flattenThreads.injectIfApplicable(node);
+    }
   }
 }
 
@@ -251,6 +260,7 @@
   infiniteScroll = new InfiniteScroll();
   workflows = new Workflows();
   threadToolbar = new ThreadToolbar();
+  flattenThreads = new FlattenThreads();
 
   // autoRefresh, extraInfo, threadPageDesignWarning and workflowsImport are
   // initialized in start.js