I've noticed on the feature wishing well other posts that suggest something similar to this. They suggest that you get notified whenever someone replies to one of your posts. That would be a hassle for people who are very active on the forums.
I suggest that instead, we would be able to follow a post by pressing a button like a star or a pen on the OP of a thread and we would get notified whenever someone posted on that thread.
ie: I follow this thread by pressing a small button at the edge of the OP. Someone replies I get a PM and/or and email notifying me that on this thread there was a reply.
It would be practical and useful. Plus, when you would lose interest in a thread you previously followed. you can just press the button again to unfollow it and cease receiving notifications.