I've started reading up on #ActivityPub. So far I had been assuming that the "@user@host" scheme was baked into the protocol, but apparently it isn't, and it's perfectly capable of integrating user-less domains into the Fediverse.
Have I misread it? (I admit I only did surface level reading so far.)
If I haven't, wouldn't this mean that instances could (theoretically) also just act as hosting providers for #IndieWeb style domain-as-identity accounts?
I've also found a whole number of interesting single-user, domain-as-identity Fediverse microblogging apps on GitHub.
At least #Mastodon also makes use of #Webfinger.
Would have to check, what would happen, trying to use something else... but as the actor should be referenced by an URL...