It breaks the HN guidelines to insinuate astroturfing unless you have evidence. Please don't do that. https://news.ycombinator.com/newsguidelines.html
People having opposing views isn't evidence of 'stealth marketing', it's evidence that the community is big and, on most things, divided. Meanwhile the "astroturfer under every bed" trope is one of the toxins that poisons internet communities—if it doesn't kill, it causes brain damage. Therefore we all need to resist the temptation to go there, unless there's really evidence, in which case you should email us at hn@ycombinator.com so we can investigate and ban offenders.