@phiofx That's all ok but why limit a service at all? Why not just leave it to the users to determine the visibility of their posts / messages? I for one want broad reach but I fully understand that some want to keep it within friends and family.
I care about controlling my online identity and content. I don't want to be tens of online identities as I am still the same person. I don't want to signup on tens of platforms. I keep my email address since I created it decades ago. And in the same sense I also want to have my content on something that I control - to an extend - instead of submitting it to someone else's service. Federation seems to be a good way for that and the opposite is a centralized service. I've used Compu$erve before.