How might portable identities work with Mastodon?
https://metalsamurai.wordpress.com/2023/03/26/more-on-mastodon-and-portable-identities/
@MetalSamurai covers this in a blog post with a remarkably in-depth discussion of the challenges and consequences of trying to make it work.
It's a surprisingly hard problem with no easy solutions. Not because the problem is fundamentally hard. Because it's not. But because Mastodon, and ActivityPub, weren't really designed with portable identities in mind, and now we're painted into a corner where now this is pretty hard to achieve.