I can see how allowing this could discourage companies from posting in these threads. I think it would be interesting to see how a hiring thread including criticism would play out, but appreciate that it would also likely invite a lot of flame wars, astroturfing and unproductive bickering.

A (different) jobs board where the companies posting the jobs do not have control of the comment discussion would be interesting to see - but would need a monetization strategy that ensures it can survive without turning into pay-to-censor junky platforms like Yelp or Glassdoor.