Maybe it's exactly the wide support for irrational but mainstream views is what concerns the author. I mean, that's what you'd expect from a conversation in a random bar, but maybe HN used to be somehow different.
I've been here for awhile, and my take is that HN both now and in the past has an unusually high signal to noise ratio, which does not mean it has little noise. It's just that noise is the default state.
