always wondered this, but kept forgetting to post it
eg users would be on @grant@toast.ooo and a community would be on @canvas@group.toast.ooo or something like that
then it would still follow the AP spec but still allow for identical identifiers (like a user account being @sc07@toast.ooo and a community also being !sc07@toast.ooo)
possibly because lemmy instances can themselves be hosted on subdomains
how I was thinking about it the instance owners would pick the subdomain the communities would be placed on, everything would still route through the main host but external interactions (like following a community) would be routed through the subdomain
eg for blahaj.zone's lemmy instance it could be setup as users sending in
@lemmy.blahaj.zoneand communities ending in@group.lemmy.blahaj.zoneor something like that