My only thought on this, is that it would need to be done carefully.
If threads are hidden in threads, which are already hidden in threads - potentially people will not know where things are or forget where things are. If people can't find things, then potentially they can't comment and it will have defeated the whole excercise.
Whether it is a coincidence or just based on popularity, some of the less popular threads at the moment are the ones hidden away.

If it is done correctly, then I think it would work well.