A "request deletion of entire mesage thread," however, would be an excellent feature.

Yep, but without relays actually deleting them, the message will come back over and over again, just to be deleted when the phone loads the deletion request locally. Nothing Amethyst can do beats a good relay.

I'm aware of the relay integrity factor. Assuming I'm using well-behaved relays, an option to request deletion of an entire DM conversation in Amethyst would be nice. Maybe just long press on the conversation thread (before it's open) and select request delete all. Saves users from having to manually request delete for every single message.