@nullkal there may be good legal reasons for blocking certain servers and on on !Freedombone you can block domains at the firewall level. But in most cases my impression is that some admins are blocking other instances for trivial reasons or because some blacklist has circulated made up by someone who was clueless to begin with.

If you have a non-trivial number of users then any instance blocking decision needs to be the kind of thing you can justify to them.