@herrabre No, the URI of an author is always portable. It is unrelated to anything and should be treated as a random string (some use it for discovery, but that is Bad(tm) and discovery is made not _from_ a URI but _of_ a URI (i.e. you find n advertised URI for an acct:user@whatever.example and then apply some verification method you trust).

It is actuallt just by chance that URIs in !GNUsocial are http URLs.