Suggestion: subscribe to topics/threads

I've found that it's difficult to keep track of threads I found interesting but are no longer highly active, especially without a search function. My suggested solution is the ability to subscribe to updates on a topic/thread (whatever you want to call it) and enable easy access to checking up on the thread for updates without having to receive a direct reply to my comment on the topic. If this already exists and I'm just blind, let me know!