Fedi moderation idea: UEFI Secure Boot.
We have a big circle of trust. We switch from denylists of known bad servers to allowlists of known good ones. You can join the trusted network if some existing member vouches for your instance, and the network effect takes over. Participation requirements include moderation, failure to moderate = removed from the allowlist. List is centralized but maintained by consortium of sufficiently big instances.
When I say moderation, I mean it in a lax sense. A single-user or small family instance is inherently moderated. Public instances will need dedicated moderators.
Requirements to participate should be lax. They're there to filter out the endless game of whack a mole with outright malicious instances. Those won't get to participate, but others will
Eventually this system can be used to enforce flag days across fedi too! "Have this safety feature for your users by $DATE or get defederated"