But (it sounds like) you’re talking about voluntary grouping, where if you dump 100 people together at a party or networking event or whatever, theoretical-person Amy will vibe best with certain types of people, and so ends up chatting up Cleo, Ming, and Kiara because they share similar interests / humor / whatever – but there’s nothing actually stopping someone from outside of that from walking up and chatting with the newly-formed group. That’s kind of what (I thought) we had now in the fediverse, where for example I can go talk about Australian news on aussie.zone, jump to lemmy.world to talk about fediverse stuff, swing by redd.that to look at Unraid updates (all communities I’m part of), but then browse the incoming feed of everything coming into my instance and view a whole lot of communities which I’m not part of, most of which I never will be. It’s (nearly) all open-by-default. Yes, there’s some blocking / defederation etc, but the default state is that users on one instance can (whether or not they actually choose to) talk to other instances.

If a new user randomly picks any instance from the top 50 (of any fediverse software, excluding maybe Pixelfed since that’s probably the least interoperable with the others) to join up on, chances are very good (but will vary based on personal interest) they’ll be able to participate in like >=90% of the conversations that they want to in the sense that their instance is federating with all the people and communities they’re interested in.

What I’m thinking-out-loud-ing (“arguing” sounds a bit more assertive than what I’m aiming for) is that this might not be how ActivityPub would optimally be used; maybe just because ActivityPub could allow 90% of users to talk to 90% of users, it doesn’t mean that’s actually the best way to use it. Maybe it serves the user’s interests better if there are clusters of “sub-fediverses” instead.

As a grounded example: Beehaw partially self-isolates from the wider fediverse (it’s not just that users could communicate but don’t; the connection is severed) in an effort to better maintain its vibe and values. I had always viewed that as the exception to the norm, but maybe having (e.g.,) clusters of instances that only communicate with a comparatively smaller amount of other instances, say the other instances in its “cluster” plus a few other clusters only (as opposed to most instances communicating with most other instances) is a different – and potentially healthier – way to architect things. So I guess partial, selective federation rather than (what felt to me like) the current goal of “if it uses ActivityPub, we want to communicate with it*”. * with obvious exclusions for spam etc.