I felt bad making a long thread once I opened Element X and saw it didn't have support for threads.

Someone let me know later that threads are hidden behind a Labs setting, but it only allows the client to reply to threads, but still exposes the entire thread inline for the channel which sucks up all the air in the chat.

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.