> I already mentioned web+ap: and then there’s web+activitypub: from silverpill (which may be the same?),
web+activitypub: is not my idea, that FEP was submitted by @jenniferplusplus. You can view proposal metadata by clicking on a small arrow button above the title - unfortunately Codeberg doesn't display this section by default due to a bug.
Also:
>Solving migration pain
>Now, as far as I know, Mastodon doesn’t have any capabilities like that, nor does any other Fediverse software.
Streams and its fork Forte have data portability over ActivityPub. These Fediverse servers use portable identifiers, it's a bit similar to what you describe, but with additional cryptographic assurances that posts on different servers belong to the same person: https://codeberg.org/fediverse/fep/src/branch/main/fep/ef61/fep-ef61.md