The problem is that you cannot get people to self-tag "this is crap / low effort". Especially not the worst actors that consistently generate garbage.

If they could do that, then they wouldn't be wasting your time to begin with. They'd have the ability to go "nah this PR is trash".

So the next idea is that we can find some sort of proxy, like whether someone used an LLM or not. But that's too ham-fisted since expert engineers with all the self-awareness also use the tool, and they have the ability and self-awareness to know that the software they are shipping is good quality, so why would they use the shame tag?

The shame tag has no audience. It's a fantasy that low quality actors will self-identify, else all sorts of societal problems would be made trivial.