So right now, we have a single user_ table, that includes fields for both local users, and federated ones, which uses dummy values for things like settings (which federated users don’t really have). This is splitting them into two tables, person (IE the person actor in activitypub lingo), and local_user.

Its a massive change because pretty much every table and code touches user_id in some way, and unfortunately there really isn’t any gain other than delineating federated users from local ones. It should make future activitypub work easier tho. I think mastodon calls these accounts vs users.