Discord also refuses to delete any data you give them. Deleting a Discord account sets a lockout flag, changes the nickname to "Deleted User" and resets the avatar to default. That's it. They don't even bother setting the user ID on your messages to something common, to a bot (and anyone who turns on developer mode) all your messages still contain your Discord ID.
I also learned from personal experience that they ignore any requests for deleting data coming in via GDPR. These people need to get slapped in a lawsuit.