If I was going to refer to the CS literature I would probably say that "ActivityPub uses an actor model style approach whereas ATProto uses a global, public, shared tuplespace"
But I wanted the mail metaphor to work and I was pretty sure everyone's eyes would glaze over at "tuplespace"
Anyway, language is this messy squishy thing but part of the success of the previous post I think was terms that allowed us to discuss differences clearly.
(And it is EXACTLY for that same reason that I am gonna dive into analyzing terminology deeper in just a little bit.)
Moving on...