Be able to remove yourself from letters you didn't create.

Hey! So I know if you want to be removed from an owl/IM/letter you can just ask the person who created it. However, in the past I have been involved in letters that were extremely upsetting to me with no way to get out, due to the creator refusing to delete me from it or where the original creator of a group letter is inactive but people still want removed. Like maybe an extra button that says 'Leave Letter' or something and a warning flashes up saying that this will be permanent unless you are readded.