It happens that the two styles are often categorized as female (agreeableness and pleasing others) and male (bluntly challenging). And indeed, in American society, men and women are in the broadest of terms socialized in those ways.
Personally, I wouldn't trade this norm for the world. I'm much too familiar with the Dale Carnegie crap of wrapping every point in senseless complements and false uncertainty to want to waste more energy on it than required. My own or anyone else's. I recognize that this preference leaves some people feeling uncomfortable. But that's my preference, and I am keenly aware that others may prefer differently approaches.
(EDIT: But read dang's comments instead. They're better than this.)
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.