Something which notifies you whenever a new comment or reply is made to a selected post/comment, so that you can keep track of any new conversation.

Something like this would be awesome as a core Lemmy feature IMO. It would essentially turn a post (or maybe any comment tree?) into a matrix style room. Lemmy is actually decent for long term discussion (e.g. helping someone with a problem), but not if there are more than two people involved.