When a post is deleted, it’s merely marked for deletion and a timer is set. Wouldn’t it be a good idea for Discourse to do the same for deleted accounts? If a mod can delete an account, and if they might be rogue, or their account compromised, all the better if the admins are notified of such an event, and have some days to respond accordingly.
More, I think one cannot delete an account which has a posting history, without first deleting the posts. Adding a rate-limit or quota to mod’s abilities to delete posts, again with a notice to the admins, would make this safer.