Decentralizing governance means that a diverse array of communities with different norms and standards can arise. For example, Mastodon is home to instances with strict harassment policies while also being home to the instance that hosts the vitriolic and far-right Gab. This is sustainable because users and servers can choose who to connect with. So, when Gab forked Mastodon or ISIS recruiters joined Diaspora, most servers simply blocked all content originating from the offending servers and accounts. Gab users can see their server and the few that are willing to federate with it; the rest of the Mastodon universe has functionally closed themselves down to Gab and its content.
via Chris Aldrich