Similar to how posts can be moved to an existing or new topic, it might be pretty cool if posts could be reassigned to a new message.
One case where this would be helpful is when a couple of users get off topic — a moderator could check off their posts and usher them into their own private area (“Get a room, you two!”). Topic is back on track and the tangential users can continue their conversation.
Sometimes it makes sense to move these kinds of posts to a new topic … or delete the posts … or lock the topic … but I’ve definitely encountered scenarios where isolating the users would be ideal.