Very few people would disagree with that premise.
The thing is that bad faith actors doing bad faith things are not going to abide by the rules on their own accord, on account of being bad faith actors. So you need enforcement, and I don't really see how HN can enforce any of the things you posted. They're not really in a position to vet anything more than you or I can.
Maybe the initial "who is hiring" post should be more explicit about the lack of moderation and vetting instead.
There's a lot of things that decent people do, in good faith, because they consider it normal and OK. If you tell people "actually, the convention here on that is something different", then I think most will respect that.
One way this doesn't work is if there's a lack of trust. For example, if an employer claims it values X, but actually behaves like Y, employees are less likely to do X, and also less likely to trust or respect the company on anything else.
Another way the HN example doesn't work as well is if the person has strong motivation otherwise. For example, if their boss told them to post a fake job on HN, and they really don't want to come back and say they can't because they just saw a new rule. But a lot of other times, the person doing the posting has more autonomy, or a more decent work environment.
A lot of guessing here, but I think stating a convention would help significantly.
Definitely some people who will disregard rules they know are rules, but I think there's also a lot of people who just thought fake job posts were the convention, and now they'll change behavior.
* done for optics, to look like growth or doing well, or just to have their name out there.
* to fill the pipeline for future needs
* to assess the hiring market, for planning
* (for reasons mentioned in article) to light fire under current employees, or see how replaceable they are
* only for a serendipitous unicorn hire, not commodity developer
* for training in their hiring process
I know all these are things that happen in general with startup job posts, though not necessarily on HN.
None of those reasons preclude "responding", but responding doesn't solve the real problem, it's only a PR sugar coating on it.
An example of disclosure on the unicorn hire one would be to simply state the truth about it. That's fine, so long as you're not pretending to grow. It could even be good optics, about hiring standards.
Disclosure of some of the other intent would preclude it (e.g., probably nobody is going to state the goal of threatening or replacing current employees). Maybe those shouldn't be done at all, or maybe they can at least say that this is a speculative post, not for a currently open position.