Every instance has an admin. They are listed at the bottom of the sidebar of the instance.

The good thing is that every team of admins can manage their instance and the communities hosted as they want.

So if an admin wants to censor a certain topic on their instance, people will just move the community to another instance that would accept it.

A good example if !piracy@lemmy.dbzer0.com, which cannot be accessed from lemmy.world.