One thing I really don't get about open social networks is "defederation" craze (on Diaspora it is more known as "shadowbanning") which is when one server blocks communication with another one.

I can get it when it happens as the last resort measure against spam attacks or other malicious interference but why on Earth any user would want it otherwise?

Would someone want cars hardwired not to drive to certain areas at all? Music players with censorship built-in blocking certain types of sounds from being played? E-mail which refuses to deliver messages to certain addresses?

There is damn blocklist (some platforms also have mute and ignore), use these as you like and stop your spreading your #fediblock bullshit. It is plain harmful for the network.