Comment by OkayPhysicist

I belong to a community that uses a chain of trust like this with regards to inviting new people. The process for avoiding the bad actor chain problem is pretty trivial: If someone catches a ban, everyone downstream of them loses access pending review, and everyone upstream of them loses invite permissions, pending review. Typically, some or most of the downstream people end up quickly getting vouched for by existing members of the community, and it tends to be pretty easy to find who messed up with a poorly-vetted invite (most often, it was the person who got banned's inviter). Person with poor judgement loses their invite permissions for a bit, everyone upstream from them gets their invite permissions back.