Oh right, maps can't be sorted...

app/soapbox/features/chats/components/chat_list.js

@@ -7,10 +7,21 @@ import { fetchChats } from 'soapbox/actions/chats';
 import ChatListAccount from './chat_list_account';
 import { makeGetChat } from 'soapbox/selectors';
 
+const chatDateComparator = (chatA, chatB) => {
+  // Sort most recently updated chats at the top
+  const a = new Date(chatA.get('updated_at'));
+  const b = new Date(chatB.get('updated_at'));
+
+  if (a === b) return 0;
+  if (a > b) return -1;
+  if (a < b) return 1;
+  return 0;
+};
+
 const mapStateToProps = state => {
   const getChat = makeGetChat();
   return {
-    chats: state.get('chats').map(chat => getChat(state, chat.toJS())).toList(),
+    chats: state.get('chats').map(chat => getChat(state, chat.toJS())).toList().sort(chatDateComparator),
   };
 };
 

app/soapbox/reducers/chats.js

@@ -8,27 +8,16 @@ const importChat = (state, chat) => state.set(chat.id, fromJS(normalizeChat(chat
 const importChats = (state, chats) =>
   state.withMutations(mutable => chats.forEach(chat => importChat(mutable, chat)));
 
-const chatDateComparator = (chatA, chatB) => {
-  // Sort most recently updated chats at the top
-  const a = new Date(chatA.get('updated_at'));
-  const b = new Date(chatB.get('updated_at'));
-
-  if (a === b) return 0;
-  if (a > b) return -1;
-  if (a < b) return 1;
-  return 0;
-};
-
 const initialState = ImmutableMap();
 
 export default function chats(state = initialState, action) {
   switch(action.type) {
   case CHATS_FETCH_SUCCESS:
-    return importChats(state, action.chats).sort(chatDateComparator);
+    return importChats(state, action.chats);
   case STREAMING_CHAT_UPDATE:
-    return importChats(state, [action.chat]).sort(chatDateComparator);
+    return importChats(state, [action.chat]);
   case CHAT_FETCH_SUCCESS:
-    return importChats(state, [action.chat]).sort(chatDateComparator);
+    return importChats(state, [action.chat]);
   default:
     return state;
   }