Earlier quoted context omitted.
It's an attempt not to have the site be dominated by flamewars.
No, it's a form of lazy censorship. Having moderators that do proper jobs is an attempt to not have the site be dominated by flamewars.
HN is a complex system consisting of community, software, and moderation. We need all three of those in order for it to function. Without software support (a lot of it), HN would be impossible.
Of course the software is imperfect, but that's also true of the moderators and (dare I say it) the community. Each needs to compensate for the imperfections of the others.