We need to rethink some UX design and processes here, not pretend low quality people are going to follow your "no low quality pls i'm serious >:(" rules. Rather, design the processes against low quality.
Also, we're in a new world where code-change PRs are trivial, and the hard part isn't writing code anymore but generating the spec. Maybe we don't even allow PRs anymore except for trusted contributors, everyone else can only create an issue and help refine a plan there which the code impl is derived?
You know, even before LLMs, it would have been pretty cool if we had a better process around deliberating and collaborating around a plan before the implementation step of any non-trivial code change. Changing code in a PR with no link to discussion around what the impl should actually look like always did feel like the cart before the horse.