> #3 is a problem to some degree on crates.io, my understanding is that they basically treat this as a human moderation problem

I think it's more accurate to say that they consider dealing with this out of scope. "I want this name that has been unused since it was added as a placeholder package 7 years ago" is not something that the human moderation will help you with. The extent of human moderation on crates.io is basically "This is malicious or illegal and was reported to us and we looked and agreed so removed it"