diff --git a/lib/types/message-types.js b/lib/types/message-types.js
--- a/lib/types/message-types.js
+++ b/lib/types/message-types.js
@@ -97,8 +97,11 @@
 
 export const messageTypes = Object.freeze({
   TEXT: 0,
+  // Appears in the newly created thread
   CREATE_THREAD: 1,
   ADD_MEMBERS: 2,
+  // Appears in the parent when a child thread is created
+  // (historically also when a sidebar was created)
   CREATE_SUB_THREAD: 3,
   CHANGE_SETTINGS: 4,
   REMOVE_MEMBERS: 5,
@@ -119,6 +122,7 @@
   MULTIMEDIA: 15,
   UPDATE_RELATIONSHIP: 16,
   SIDEBAR_SOURCE: 17,
+  // Appears in the newly created sidebar
   CREATE_SIDEBAR: 18,
 });
 export type MessageType = $Values<typeof messageTypes>;