We – of course – care about manipulation on HN; the only reason this is a site people come to for discussing so many different important topics is that so much effort has gone into ensuring integrity in the content that can be read here. It's just not that easy to engage in astroturfing, shilling, brigading, etc without setting off alarms either in the software or in the many HN users who have finely honed bullshit detectors, because organized, manipulative participation looks and feels so clearly different from earnest participation.