I say that based on looking into literally thousands of such cases, and spending god knows how many hours poring over data. My comments are based exclusively on what I know about HN—I know nothing at all about other sites because I don't have their data. But I know a lot about HN, and I can tell you that the users making breathless insinuations about this stuff have literally no idea what they're talking about. The truth is just painfully boring. (Edit: here's a detailed explanation - >>27397230 .)
As for why the comments in such threads get downvoted, that is easily explained by the fact that flamewar topics attract shitty comments, and shitty comments get shittier as people get politically and nationalistically riled.
This is a really insightful way of describing this phenomenon.