The comment you linked to added to the conversation just fine. That it was downvoted seems churlish.
Negativity per se isn't a problem, but gratuitous negativity is. We've been planning for a long time to add something to the HN guidelines about that, and are likely to do so soon.
It may be helpful to explicitly differatiate negativity vs. gratuitous negativity in that case. (Most examples of gratuitous negativity I've seen are low effort "this site sucks" comments, which are downvoted for reasons unrelated to negativity, and ad hominem attacks are already in the guidelines.)
Negativity per se isn't a problem, but gratuitous negativity is. We've been planning for a long time to add something to the HN guidelines about that, and are likely to do so soon.
Edit: Very soon. https://news.ycombinator.com/item?id=9317916