Sometimes people start threads in unrelated channels. I would be great to move a chat or a thread from one channel to another one; or at the very least, to copy the thread from one channel to another and then have the option to grey out, relate or deactivate the thread that should no longer be added to.

Another use case is scope creep. When one thread suddenly moves from the topic at hand to a whole other conversation that should really belong in a different channel altogether.