One of the primary ingredients of the “Mastodon reply guy” phenomenon, one I think does not always necessarily come from a place of ill will, is a kind of online solipsism. The UIs of social media apps invite us all to think that we’re in the room with •everyone•, that •everyone• sees us, is talking to us.
It’s a bit like the parasocial relationship of the singer who “just knows me” but has never actually met me. This design of this space makes us forget the nature of our relationships.