That also works. We're doing stuff like that with Orly, where you have your follow list as the guide and it figures out the mailboxes for all of your follows and looks for their stuff over there. That's more personalized and dynamic, but communities usually have some core relays, that are like hubs.

They do. But to me the "hub" is just the "hint" on how to get most of the posts/member information. Reaching out to people's outbox and inbox relays will bring more stuff that wasn't sent to those core relays.

But it does make things very complicated when you consider everything users can choose.

No, just like outbox, that puts responsibility at the wrong level. What is wrong with Community admin just doing their job? They're value prop = taking care of hosting and moderation. Why take that away from them? And give it to the actors least incentivized to do a good job. Guaranteeing a crappy, non coherent experience for everyone involved.

Because admins don't get to choose what I say in their community. They only choose if I can post in the community relay or not. I can create community events anywhere I want. Which means clients can be built to show the "real" community that is not moderated. Which also means that clients that only bring moderated events will be bashed for censorship by members. I have been there. There will be conflicts between admins and members and when those happen, it's the clients that will suffer.