Quoting dang

Spam, and its cousins like content marketing, could kill HN if it became orders of magnitude greater—but from my perspective, it isn't the hardest problem on HN. [...]

By far the harder problem, from my perspective, is low-quality comments, and I don't mean by bad actors—the community is pretty good about flagging and reporting those; I mean lame and/or mean comments by otherwise good users who don't intend to and don't realize they're doing that.

— dang

actors community good hackernews isn low marketing mean moderation orders perspective quality reporting spam