I thought his point was mostly about the credibility and influence carried by negative comments on HN - probably thanks to both its link to YC and the presence of highly regarded industry figures in the comments. So a negative comment on HN might have a more tangible effect on the man's professional life compared to a negative comment on, say, reddit.

Disclaimer: I honestly don't know how bad things used to be. By the time I started visiting HN in earnest, dang et al. were in charge, so I'm assuming a fair bit of moderation takes place now.