This is probably impossible (or really hard anyway...), but I'm thinking of a script that can detect when a reply has been posted to a thread and displays a toast message that links directly to the post. I don't like the fact the when the topic subscriptions email you as it means either wasting time checking emails, or just coming onto the forum and searching each topic for new posts.
If it can be made, it should be possible to have a list of "Watched Topics". It's just an idea, hopefully it's possible