I'm about to implement replaceable events in nostrdb and just had an idea that fix the contact-list unfollow problem for good:

when replacing a note with a new note, generate a "delta", which is the difference between the old and new note (tags, contents, etc).

This delta can be quite small, so it can be done automatically for all replaceable events.

This would enable any nostrdb app (damus ios, notedeck, etc) to "self-heal". it could detect simulatenous follow and unfollows and discard the unfollows.

You could also use this to show diffs in longform posts, and follow/unfollow histories for all users in your local db.