I believe the Activity tab used to work — or work better. It showed, IIRC, which threads where having comments added most energetically, or something like that. It was a way of seeing which topics were being “bumped to the top” by people who were making comments. I think the system went through an upgrade quite a long time ago which caused the Activity tab functionality to fail and it was never fixed.
Yes! I used to use it all the time. It gave a good indication of what topics were “hot”. After an upgrade years ago it quit working.
You are correct as far as I know. It used to be a way to look
at a listing of the threads and would show the total comments
thereon. Now total comments are shown on the “Latest Articles”
I do remember when a thread showed how many people had viewed it or responded to it. Used to be up in the 1000 - 2000.