I agree with your second paragraph completely, and I would be averse to comments whose only content was "niceness". I'm on LW for intellectual discussions, not for feel-goodism and self-esteem boosts.

I think it's worth distinguishing niceness from respect here. I define niceness to be actions done with the intention of making someone feel good about him/herself. Respect, on the other hand, is an appreciation for another person's viewpoint and intelligence. Respect is saying "We disagree on topic X, but I acknowledge that you are intelligent, you have thought about X in detail, and you have constructed sophisticated arguments which took me some thought to refute. For these reasons, even though we disagree, I consider you a worthwhile conversation-partner."

When I began this comment with "I agree with your second paragraph", I wasn't saying it to be nice. I wasn't trying to give fubarobfusco warm fuzzy happiness-feelings. I was saying it because I respect fubarobfusco's thoughts on this matter, to the point where I wanted to comment and add my own elaborations to the discussion.

There's not much purpose to engaging in an intellectual discussion with someone who doesn't respect your ideas. If they're not even going to listen to what you have to say, or consider that you might be correct, then what's the point? So I think respect is integral to intellectual discussions, and therefore it's worthwhile to demonstrate it verbally in comments. But I consider this completely separate from complimenting people for the sake of being nice.

It sounds like part of what Submitter B is complaining about is lack of respect. The guys she dated didn't respect her intellect enough to believe assertions she made about her internal experiences. I suspect this is a dearth of respect that no quantity of friendliness can remedy.

(For what it's worth, I'm female, albeit a rather distant outlier. I'd emphatically prefer that "niceness" not become a community norm. For me, it takes a lot of mental effort to be nice to people (because I have to focus on my internal model of their feelings, as well as on the discussion at hand), and I get annoyed when people are gratuitously nice to me. This post makes me wonder if I'm unusual among LW females in holding this opinion.)