Is someone paying to get upvoted? Almost certainly, but I doubt it's worth a lot here where the sorting algorithm is much more opaque than Reddit. On Reddit getting to the top is just a numbers game.
Also, even though there's far too much political posts on HN, they're the minority and I can't see a reason for some secret government agency to pay staff to change our views about the political world. Reddit is much more politicised, and it'd be naive not to assume every major government has a propaganda team of Reddit posters.
(I'm using Reddit as another example of popularity-contest forum like HN is)
The only real question is "how many", and "is that enough to render the discourse on HN worthless?".
It's hard to quantify, but in my many years on HN I have not noticed a very noticeable change in the quality of discussions on topics that I follow closely.
Whatever happens speak your mind, you've earned it by existing. Don't get discouraged by downvotes. The future depends on it.
For gov examples, try starting a discussion about America's torture program, war crimes, or independent anti-war media. Your post will be flagged, and it won't get back up because such discussion 'goes against the guidelines which are actually rules'. The moderation will be praised by high karma accounts, who are quite happy with the status quo thank you very much.
Check out any thread ever concerning Assange. Those comment sections are masterclasses in the derailment of productive conversation. Since pointing out obvious shills is against site rules, you're more like to be banned for pointing out meddling than for spreading outrageous smears.
For "Big xyz", try writing a comment about GMOs, or agricultural pollution, monopolies, enviromental destruction, the not too distant horrors perpetrated by pharma co's, or any of a number of other third rail topics like unions or healthcare costs. 'Totally normal accounts' will slither out of the bushes and sealion your thread to death.
Yes, it matters - a lot. "The smart way to keep people passive and obedient is to strictly limit the spectrum of acceptable opinion, but allow very lively debate within that spectrum." - Noam C
Or maybe the recent resurgence of Javascript frameworks in Web, desktop and mobiles is a plot of Russians to slow the computing and software engineering for the westerners by manipulating online tech communities?
I often check an account and notice it was not active for a substantial period of time before a sudden change in tone is noticed.
Seeing the same anti-vax talking points (for instance) spread from Reddit to here has been upsetting. The main difference I have noticed is the responses here are more sound technically, typically, call out the flaws more quickly, and are obviously not being influenced by the astro turfing. It's still tiresome, but here we are.
A while ago the comments were the gold, now I can't really get them. In my subjective experience, contradictory comments (to the post) became the most popular. That doesn't make sense. You can't contradict always to anything.
So HN became like any other new site: I'm skimming through the headlines in a minute, and done.
If into this sort of analytics, we are always looking for data engineers and data scientists for Project Domino - see our DefCon AIV keynote for more info.
EDIT: In the case where someone says something against common perception, downvotes in particular deemphasize it (turning the comment gray on HN, collapsing it on Reddit) as this comment unintentionally demonstrates, thus why astroturfing in such forums successfully can be hard to do nowadays. The real astroturfers do Facebook/Twitter instead where content can't be downvoted.