One thing to consider is whether communities explicitly defined allow for taking the concept next-level on the fediverse.
Now it is mostly implicit i.e. instance boundary, discourse forum, etc.
An explicit definition as a domain model, allows modeling things on top of that when needed, such as Membership + Roles, or Governance.
( @hamishcampbell started talk on the latter which - if federated - would require a meta-model AP extension to define policies. See https://socialhub.activitypub.rocks/t/what-would-a-fediverse-governance-body-look-like/1497/51 )
@humanetech @hamishcampbell This is all very much of interest to me. Are you aware of my "neighborhoods" work? (It's not a formal proposal because I'd rather build it first, see how it works in practice, and then make a proposal)