I’ve noticed a small imperfection (not exactly a bug) that I’d like to mention:
When acting as an admin and splitting a private message (i.e., moving selected posts) into a new conversation, it’s currently impossible to add yourself to that new message. As a result, the conversation won’t show up in your inbox, making it hard to find later. The only way to include yourself in the new message is to reply in that conversation (which you might not want to do often).