It happens to me very often that I see an interesting question that I'd like to know the answer to. I'll favorite it but then never get notified if there is a change. It would be very nice to have a "subscribe to question" feature, which sends me a notification if there is a new answer (or optionally an edit to an existing answer) to the question.
I don't know to what extent this is even within the realm of possibility for physics SE, as it's part of the larger SE framework, but I thought the idea might also be useful for other users, and didn't see this mentioned on meta.