How about mentioning in the who's hiring post that people can email HN if they think someone posted in bad faith. The slight inconvenience should turn off people who complain just for the sake of it, and other readers won't be discouraged by seeing the complaints. The downside is extra admin for you, of course.
I don't think I can handle many more emails*. But beyond that—what would we do? We don't have the cycles to arbitrate these things; nor the skill; nor the interest.
* was going to make a Mr. Creosote reference but thought better of it
Hn/jobs may not have the interest, sure. Job posters in general may not have an interest. I think monetization here comes from candidates. As a job seeker I would be willing to pay for access to a job board where listings/posters are somehow vetted to protect me from filling out ghost applications.
