alt Hacker NewsPeople like to talk about Jane Street because it is this Very High IQ™ company that pays people astronomical salaries and is extremely hard to get into.
They don't have to do marketing, though. It's not like they sell anything to Hacker News readers, they make their money trading finantial assets
You don't think that companies who want to hire engineers ever try to post stuff to Hacker News as a way to market themselves as a potential employer? Where did you get this impression of "Very High IQ" and "astronomical salaries"? I'm guessing at least part of it is from reading stuff from them or from talking to other people who read stuff from them.
The fact that you seem to adamantly disagree that there's any plausible angle here doesn't mean it's not marketing, but it might mean that it is marketing and that it's working on you.