I think that's the point though? Plenty of things not worth engaging with also aren't technically violating any rules: but wasting the brainpower on them also isn't worth it in a reliable way.

That's where an ignore system is useful.

Sure, I was just addressing the apparent dissatisfaction that some accounts remain active despite posting “moronic” comments, and pointing out that we can't moderate according to our judgement of someone's comments being “moronic”, only the guidelines that everyone on HN agrees to be governed by. To expand on that: “moronic” will mean different things to different people depending on their worldview; whereas the guidelines and our application of them need to be defensible, regardless of the position.