Note: This is not a duplicate of Is there any way to favorite/bookmark an answer?, since I am asking specifically about receiving notifications, nor is it a duplicate of Adding Favorites to the Stack Exchange global inbox, since I am asking about a separate facility to tag individual questions.
I'm asking this from the context of Puzzling.SE, although I'm sure it could be relevant for all SE sites.
Often, on Puzzling, a difficult puzzle will be posted. I will look at it, and think, "That's really interesting; I'm curious to know what the solution is." Sometimes I will favourite/bookmark it, and continue to go back to it to see if anyone has posted an answer/comment.
What would be much more helpful to me, is if I could click something that would add that question to my SE notifications, so I get notified when someone posts an answer or comments, in the same way I get notified for my own questions. Since people use the "favourite" functionality for different things (as a temporary bookmark, or as a way to keep a list of best questions, or as a way to give kudos for an excellent question), it doesn't seem like it should be used for this. Rather there should be a separate "flag" of some sort that can be applied.
Once I lose interest, I could uncheck it, and I would no longer get the notifications for that question.
On Puzzling there are also often puzzles that are worked on in a "group" format: There are many bits to the puzzle, and different people offer solutions for each bit. Thus it would also be beneficial to receive notifications of edits on answers I have tagged/flagged/marked. I realize this aspect might be more difficult, since it doesn't mimic the notifications supplied for my own questions, but even if the notifications of answers/comments could be implemented, it would be very helpful.