Imagine if, when you refreshed this HN page, only comment chains you’re already in would refresh timely. Yes, this would “work” to some extent, but it would clearly be a regression.
Additionally, going viral can overload your server due to this architecture. In ATProto this never happpens for self-fosters (of PDS) because the cost is amortized by AppView. (Same as in centralized products where the cost is on the backend.)
(To be honest, I'm already surprised that Mastodon scaled as far as it did. I will say, if I had seen the state of the web's architecture 20 years ago today, I probably also would have claimed that it was inherently insecure and that there was no way to get it to be secure enough to scale to billions of users, so... I don't know, maybe people will keep finding duct tape solutions to make it work, worse-is-better-style.)
I'm not super up-to-date on Mastodon's/ActivityPub's workings, but aren't replies to a post pushed to the original poster's server? So wouldn't followers then be able to pull from that server at any time to get an always-up-to-date view of replies, at least theoretically? (With maybe posts from the last few seconds missing if the network's slow.)
(Asking because I've seen you claim that the architecture is inherently limited to never be able to achieve the "cohesive" experience.)