There's a world of difference (But little way for a third party to tell apart) between:
A paid shill.
An unpaid troll.
Someone who genuinely believes what they are posting, because they do not have the same information you do.
Someone who genuinely believes what they are posting, despite having the same information as you, because they prioritise different bits of that information differently. That is called a 'political opinion'.
For reference, I have been called a CCP shill at least once. I have never been to China, I have no affiliation with the CCP, I am not trolling, and I have not received a penny for posting nonsense here.
Again, for casual readers: Chinese people in the US who don't support squashing democracy fighters in HK (I think/hope that's the vast majority of them - maybe more hope now that I'm being downvoted) are awesome.
Surely, "I'm confident I'm not gullible" is the primary risk factor for actually being gullible.
At least, that's how I see it...
Fortunately, HN was also blocked where I worked at the time, so I already had a proxy set up. That worked fine. How subversive of me!
Which, we could say is because brainwashing since youth and perhaps there is some truth to that.
But I think likely the biggest thing is the same thing that motivates everyone else. Self interest. They want to see an expanded China with greater say in world events and greater share of the economic pie. Because it would benefit them. They see disruption or anything anti CCP as contrary to that goal.
The trouble is that most "calling out" that people do about this is easily seen to be bogus, even from just the public records of the commenters—unless you believe that Chinese (or, before that, Russian) moles were posting, say, GitHub projects in 2013 so they could get away with propaganda 6 years later. A lot of what we do as moderators is simply to sift carefully through the publicly available information. It's an indication of how lazy these accusations are that the users making them mostly don't bother to do that.
It's a cheap shot to fire off "you must be a shill-spy-astroturfer-bot-troll" in an internet argument. It degrades discussion, and the overwhelming majority of the time, there's no information in it beyond "I don't like what you say". The users who do this need to learn how unreliable this impulse to denounce others is, and restrain themselves from letting those neurons fire. Not only does it degrade the community in general, it often targets individuals in ugly and distressing ways, which none of us wants to see here. For an example, see https://news.ycombinator.com/item?id=19403358.
What Twitter and Facebook are writing about in today's posts is something completely different. The fact that such manipulations exist does not give HN users license to cheaply smear each other. Both are wrong.
I'm pretty sure this was the podcast where I heard that: https://samharris.org/podcasts/145-information-war/ (Relatively near the beginning of where the guest comes into the podcast, if I remember correctly.)