I just tried to use the Thread Tools->Subscribe pulldown to join a thread, and it didn’t seem to work, judging by the lack of the thread appearing in my subscribed list.
Just thought someone should know.
I just tried it and it works for me.
Do let us know if the problem persists.
I just tried it again, and it worked.
The bad news is that I now know why it didn’t work for me. The answer is too embarrassing to tell, but the upshot is that I retract my original complaint.