I'm sure they're afraid that people will bash certain companies in them. But I'd like that too. They should let the company moderate the discussion in those posts. I don't care if they're highly censored, I think there would be a lot of value to being able to ask the company questions about the roles.

The job postings are basically ads due to the fact that YCombinator runs the site for free. Considering how often someone posts a comment that is mean spirited and possibly even wrong which gets to the top I don't think that allowing for discussion would help at all.

Unlike everything else on the front page of HN, job posting are not there to be "interesting". Before the current system, when people could comment on them, "interesting" quickly became a problem.

They'd be more interesting if they weren't so cookie-cutter. "Help us disrupt the X industry". "Passionate about [insert particular software thingy], so are we".

At one point, I believe it was said that one reason discussion isn't allowed is so that stealth companies hiring aren't outed in the comments.