There is. There is banning and shadowbanning, which includes mechanisms where whatever stories someone posts are "dead" on arrival. HN has robust mechanisms against spam. Re "manipulation" I'd think one person's manipulation is another person's posting interesting stories, but as was said, if someone's submissions get flagged enough, it will get attention and their posts will be killed if deemed spam. Overall I think it's more common just to see posts that people disagree with or read into versus actual "manipulation".
Also, the concept of manipulation is very insulting to the readership. Maybe it's sometimes warranted, but on HN of all places, I think people can debate, judge, and flag on their own if they think something is being manipulative.
The suspicion of manipulation is based on years of evidence of "troll farms" and other social media campaigns. To think that HN is immune is naive.
If arguably the smartest tech group on the internet cannot devise a defense, then we're more doomed than I thought. After all, at the opposite end of the spectrum we have "AI" at Google and other companies banning users based on incomprehensible algorithms. Surely there's a path between the extremes.
Consider for a moment how little it would cost to pay people to post on HN. Other HN readers don't even need to see it; it just needs to get indexed by search engines. That adds the weight of HN to the content which it is linking to as far as the search engines are concerned. They probably aren't measuring HN reader votes.
So the question is, should we allow HN to be used as a lever to promote anything that a financially-backed group wants to promote? Or can we devise ways to reduce or eliminate this?
Also, the concept of manipulation is very insulting to the readership. Maybe it's sometimes warranted, but on HN of all places, I think people can debate, judge, and flag on their own if they think something is being manipulative.