I think (and have been saying this a bunch lately) that he's right about ActivityPub and Mastodon, and that "a universal timeline" is actually a really good way to put words to it. I was a Mastodon hater for years, but having used it for the past month or so with an actual community of people (really: the whole community I interacted with on Twitter before), I have to admit it: the ActivityPub people were right about…
I just hope the last few people I follow on Twitter who I really enjoy following move over too. But unfortunately that's "Space Twitter", so we will see...