when i ran a fediverse server for myself and 3 people, but allowed public signups if someone came by; it was very easy to ban people, and very easy to null-route entire swaths of the fediverse, because i didn't want their content on my service.

That's more what i got from that pull-quote. I know a company that has hundreds of individual forums, and those are all moderated quickly and correctly (last i heard). They're moderated so effectively they often get DDoS by Russian IPs for banning users for scam posts from that country.