Also this is a FINE example of why niche communities need unbiased online infrastructure. A casual google-searcher may judge them by whatever google's AI decides is representative of the group, and choose not to deal with them at all.
For other differing rules, instaces generally silence from the federated timeline. Eg: I can still follow Humblr.social and Sinblr users, but Federated timeline users won't have to drown in porn if the admin silences the server.