I don't see an "unsubscribe" option in thread tools.
But I see it in the other forums.
That's interesting. I have an unsubscribe option in the threads I've responded to in Pundit's forum, so perhaps you're not subscribed to the thread where you tried this. There might also be a link in the emails that get sent out, but I don't really read those before deleting, so I'm not sure.