@jsit @ben @timbray
The idea has merit. spitballing - Maybe my instance can belong to multiple of these trusted rings of federation.

Maybe getting in is like a handgun waiting period in the US, 5 day waiting period to federate, relatively small (25$ usd) one time deposit upon application unless you're sponsored by an instance/admin in good standing with the group. Both methods weed out the low effort harassment instances.

I could see our instance as part of a small self-hosted instance ring and also a regional instances ring.

A resulting question: who decides what behavior gets your instance kicked out of the ring, in a timeframe that allows a rapid response and defederation by all parties within the ring.