Looks like data/account portability is in the works: https://swicg.github.io/activitypub-data-portability/lola

But at ATProto/Bluesky, account portability was a consideration from the start.

Email has federated pretty reliably. Granted, it's nearly impossible to host your own server, because the rest will automatically assume you are only sending spam, but the well-known servers all federate quite nicely. Worst case scenario is that some organizations put a footer on outside messages warning that it's not internal.

They mean start posting, viewing and interacting in it.

Rumors of the death of the fediverse have been greatly exaggerated. I'm following a vibrant community of nerds, creators, writers, game developers and interesting people on Mastodon right now, and there are numerous other platforms on the fediverse as well, with their own communities. Lots of people have been able to decide on one or more instances for themselves. I don't know why it's such an intractable problem for HN.