I’m still trying to understand all this. I thought all instances “see” (federate) each other. If they can defederate (block) others from seeing an instance, isn’t that going to make discovery a problem? Wouldn’t that also mean I need to create a new account just to see that instance?
Defederating only affects your instance and the other one, so it only affects users on your instance and on the other one (who cannot see content on your own). To get around it requires another account on an instance that has not defederated.
Even aside from differences in opinions, there are very valid reasons for defederating. Some places do not control spam bots, for example.
Most instances default to federating with any instance they find out about, but there is also the ability to make this a whitelist instead and only federate with specific servers.
