Comment by Arathorn
this is wrong - the threads support in labs lets you create threads and navigate into them as you expect.
what you are describing is the old threads workaround which predates the proper solution in labs which should exit labs asap.
I am describing what I see on Element X on iOS today. If someone replies to threads, it is not hidden and navigable on this client. Even after switching the labs feature on, the app was showing the thread interspersed with the rest of the conversation.
Uninstalling the app, reinstalling, and making sure the labs option is turned on before navigating to a room with threads, is behaving how I expect.
So maybe, its a bug that the room does not re-render after toggling that setting.