Gregory's Server
It doesn't always work that way in the greater Fediverse.
I tried out a nice Lemmy instance. I found a nice discussion group with one of my interests. I couldn't join it because the Lemmy instance I was on was defederated (rightfully) by the Lemmy instance I joined.
In other words, to block out handfuls of people, other people were cut off from good people, good groups.
Given the number of Mastodon admins who have shut down instances whimsically and the many more Mastodon admins frequently threatening to defederate other instances I wonder what problems will come to Mastodon in the future.