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.