Vivian (they/them)

I love that I managed to guess quite a few of these

Well I’d say most of them are federated together, or at least those with a good amount of users. In practice you don’t really get islands other than I guess troll instances that everyone has blocked.

And AFAIK as long as an instance isn’t blocked by yours (and vice versa to be useful), you can follow a person on that unfederated instance and it should just work and get federated.