This idea is simple.
We’re updating the guidelines to add:

“Avoid gratuitous negativity.”

Critical thinking is good; shallow cynicism, on the other hand, adds nothing of value to the community. It is unpleasant to read and detracts from actual work. If you have something important but negative to say, that’s fine, but say it in a respectful way. Negativity isn’t the problem–gratuitous negativity is. By that we mean negativity that adds nothing of substance to a comment. This includes all forms of meanness.

~ Sam Altman, New Hacker News Guideline @ Y Combinator Posthaven