Well, since you don’t mention boundaries, it could be very different to todays platforms. For example every ‘instance’ is just the frontend/entrance to the same, decentral network that stores the data. Your username would work on every single one of them and it didn’t really matter which one you picked.
We could also do away with the moderators and have it a democratic place. We could either all vote on decisions or delegate our power to other individuals and keep something like moderators/sheriffs but elect them democratically.