The notify button should work. Is it alternating between notify and un notify as you do each action?
Yes. The only thing that did happen when I tried to Notify/Unnotify was that I actually got an email when someone replied in a thread. I think this was true on both desktop and mobile.
However, I did just try again on the "Skateboardle" thread. I hit the Notify button, it then changed to Unnotify, and I hit it again. I'll check to see if I still get replies.