alt Hacker NewsPeople will need to participate otherwise there won't be any new content. I see it as just like vouching, except someone has to vouch for green accounts. A slightly more equitable (and easier to implement) version of lobste.rs' invite tree.
What I want is for green accounts not to be abused as much as they are. The number of noxious, vitriolic troll alt accounts and bots is getting ridiculous. That is almost entirely the fault of established users of course, but there's no way to deal with them poisoning the well without affecting new users.
I think you missed @sltkr's point. HN wouldn't just have less new content; it would fail to develop new users. That kind of stagnation is how sites like this die.
Aggressively filtering to raise the average post quality is a sugar rush and it has the metaphorical long term consequences of type-2 diabetes. Things start out feeling great but the acceleration of death is effectively guaranteed.