No you’ve got the issue slightly wrong. They’re on server x, but are creating alts on server y and spamming the fediverse with those alts.
Server x is already widely banned, but they can still coordinate among themselves there. The wide openness of server y is allowing them to pollute the fediverse.
Ootl, what was wrong with kbin that led to the fork? I thought Ernest had quite a bit of support from the community