On HN the goal is to gratify intellectual curiosity, so we're looking for a sweet spot of, let's call it, playful substantiveness. Under the constraints of internet discussion, it's difficult to get there. Environments become boring when they're predictable, for example predictably negative or predictably positive. At the same time it's obvious that intellectual curiosity will fare best in a culture that is welcoming to all, since if we exclude some—whether actively or passively—we deprive ourselves of the intellectual curiosity they would otherwise bring.
I do think HN's culture falls short in this way. We can't fix that by imposing any formulas, e.g. a positivity rule, because that would make the site more predictable and thus more boring again. The fixes need to be more subtle.