It's not one of the biggest and it's owned by one individual, so they can ban who they want. from the about: "hello this is my 'general purpose' instance, hosted in europe. i made it in 2017 to have a good and stable space for myself in the fediverse, and welcome everyone who felt safer here. a feminist, anarchist, communist, cyberpunk culture and many trans and queer people, often with tech or scientific interests."

"One of the biggest"? I looked at the instance, it is octodon.social, which does not even make top 50.

These people have an app called Twitter don't they?