As soon as someone from there follows you. Post federation is based entirely on that.
The bootstrapping process here is social, not technical, and usually looks like "follow a few people and some of them will follow you back and boost your stuff".
Since you asked about .art specifically, I run a single user instance and I can follow people there. I'm pretty sure they just blacklist aggressively.
There's also relays which will send out your posts (assuming your instance is subscribed to a relay) to all the other instances (but not users - this just puts them in the "federated" timeline, not individual ones) subscribed to that relay as a kind of "wider Fedivee view".
Which might be a significant barrier. Non-tech users might have no clue who sees what. If ServerA can talk to ServerB. etc
That's kinda the part i'm questioning though. You as a user have to look at how each server handles federation to know what is visible.. maybe?
For sake of argument, it might be possible to one-way-federate. Ie read posts from mastodon.art, but if i reply my post might not be seen by mastodon.art users. This is just an example, i have no clue, but i'm illustrating where confusing could arise as rules get more complex on how federation works.
Hopefully it's black and white. If i as a user can see mastodon.art posts, then they can see me. Anything more complex than that (like one-way federation) would be prevented by the software for sake of a simplified UX.
Maybe an instance blocks you. Maybe not. Fret not, it will be ok; you will have interactions with other people anyway.
Ie imagine mastodon.art has a good Blender community. I'm joining Mastodon for exactly that community. If i join mastodon.social, i may as well .. not. It's blocked by mastodon.art. It's not even worth my time signing up if my goal is to be part of a specific community.
I'm not trying to build a general audience or have my general posts heard by the public. I'm trying to be part of a specific community. Federation seems bad here, if the community you're interested in is not fully open at least. As mastodon.art most certainly is not.
> I’m not trying to build a general audience or have my general posts be heard by the public.
> i’m trying to be part of a specific community.
> Federation seems bad here if the community is not fully open.
these seem to entirely contradict each other.
Because the community is closed, currently lol.
> these seem to entirely contradict each other.
Yea, i think we agree? My point was (roughly) that Federation contradicts being part of a community if you rely on Federation to be part of the community.
Ie don't use federation if you need to be part of a specific community. And in my case, well, i guess i just don't join lol. If the community is at max capacity, too late. Maybe one day they open, but such is life. Federation isn't designed for this, it seems, and that's fine. "This" being, distributing a community. It seems communities are centralized.