Follow a community thread and hear when it moves

In a client's community, people ask a question, leave, and never see the answer. The thread looks unanswered to everyone else, and the person who asked opens a chat later with the same question.

Members should be able to follow a thread, automatically when they post or reply, and hear when someone replies or when an answer is accepted. A daily summary would be fine too, it doesn't have to be instant.