I have a problem with the 'likely' part, because that's where the 'paranoid' comes into play.

What evidence is there that it's likely, other than paranoia?

If you were to be assigned to astroturf certain demographics, what better target than HN would you chose to reach tech-professionals?

That's a fair point, but as evidence of likelihood, it's still kind of weak. The US government might post here. But then again, so do communists and anarchists and libertarian capitalists and what have you. It's not as if HN is awash in pro-US, pro security sentiment anyway.

It seems to me as if the purpose of bringing it up is to warn people that any opinion they encounter of a certain kind can't be trusted, because it's probably part of a coordinated campaign of government manipulation. That's a couple of steps away from calling it thoughtcrime.

I haven't seen a political comment thread on a major site which hasn't been polluted with astroturf in the last 2 years or so. Anything regarding Russia is particularly obvious but they are all at it. Then again, when enough regular commenters are just parroting talking points there's not much distinction.