From what a quick research brought up, it seems like Mastodon distinguishes the authentication entity (user) and the identity entity, while Pleroma combines both in a single entity.
(In the Mastodon schema the
users table has an
account_id column whereas in Pleroma the
user entity has an
(Authentication here in context of instance-local authentication using, for example, username and password.)
For ForgeFed and implementation of it in existing forges there were some similar discussions on what way is better suited for which situation. And, IIRC there a third approach came up, which stores remote users in an additional entity.
So, my question is, what are your arguments for using one or another?
I’ll share my view in a reply so it’s a little bit separated from the question itself.