It would be annoying to lose your instance, true, but you just move to another or roll your own.

This is a problem nostr solved, and I believe bluesky solves as well though idk as much about the protocol. On nostr, your identity and your instance are different things. Relay goes down? There's no meaningful impact to you. You're typically connected to several, each of which store your content. You identity isn't username@somerelay dot com, it's just username.

As a user, I had this happen to me early in mastodon and it was very frustrating to lose all my follows, followers, tweets, settings, etc. I realize there's now ways to manually backup etc but properly moving an account requires a cooperative instance which can't happen if it's de-federated or just drops offline randomly like mine did.

The Fediverse and ActivityPub will continue to evolve, but unlike SMTP, they were created after the internet became adversarial. This author isn’t the first to try to fearmonger over the future of AP, and they won’t be the last.

This isn't fearmongering, it's him reviewing the ways SMTP tried to solve the spam problem and became centralized as a result. These questions of how we tackle spam and moderation are valid, important questions. And Fediverse, at a structural level, is basically the same as SMTP. We have users at instances (e-mail hosts), they can send messages/tweets/links (emails) to users on other instances. Each instance is free to accept/reject messages from other instances based on their own criteria. That's the whole thing. That's exactly how SMTP works.