And the mundane reality is that they won't use it for blackmail or in any such personalized fashion (except for government requests). What they will use it for, is training language models. That's the new way of monetizing "user-generated content", especially one you've managed to lock up so it can't be casually scrapped by anyone else.

Don't forget that if you do decide to delete your account its simply renamed not purged.

One of Discord's shareholders is Tencent (not Microsoft!!), however, the co-founders are still on the board and are highly occupied with day to day stuff. Message deletion on Discord is traceless from the outset (once deleted, no one, not even database admins, can retrieve deleted messages; the same thing also applies to the metadata, but not messages, of deleted users), in fact, this is one of the features they are bragging with. Traceless deletion is verified by both engineering related blogposts and interactions with support.