Allow bulk-deletion of my messages in communities I am no longer part of

Right now, I can either individually delete messages I posted that I can still access, or I can hit the nuclear "delete everything" message. The latter is usually too extreme, but if I parted with a server on bad terms, I may not want to keep my messages there around forever with no control over them.

Add more fine-grained ability to bulk-remove messages, including from server I am no longer part of