That could certainly be. The trouble is that we have no way of sorting out which companies are doing what—there would need to be some kind of 'due process' whereby the community could assess the fairness of different claims, and Who Is Hiring threads are no place for doing that. So in the end we just ask people not to post these.
It's not to deny that these things are a problem, just that it can't be fairly decided here.
Suppression is actively affecting people, though I'm not sure how harmful it is yet. There's already self-moderation happening (community votes), so again what is there to gain?
No one is asking you to pass judgment. I’m a long-standing member here telling my truth, and preventing me from warning others is reprehensible imho.
There might be vindictive posts but people could judge them on the merits of their argument and history. But you are going out of your way to prevent expression. What is there to gain?
How would you know if the see-saw tipped and the problem is more pressing when HN users are advised not to reply to job posts to complain about something?
Should users reply somewhere else or email HN directly? Should users accumulate karma and downvote or flag the posts? Care to put this in the text on top?
It's not to deny that these things are a problem, just that it can't be fairly decided here.