kbin.social administration controls only what is published on kbin.social, and what content from elsewhere kbin.social users can see. An user banned from kbin.social can make another account, on another site and start recreate there his banned community. kbin.social will be able to ban this remote user and remote community, but this restricts only what kbin.social users can see.
Exactly the same for another /kbin or lemmy site - just replace the domain name accordingly.
themadcodger
Eggscellent