Don't you know? Everyone on Hacker News is a bot. Even me. Even you.
\end{jest}
More seriously...
The thing about propaganda is that once someone starts believing it, that someone can potentially (and often does) spread it organically. Hacker News can inadvertently be a hotbed for propaganda spreading of all sorts without even a single bot or paid poster/commenter. I know I've fallen victim to that before, parroting something that ended up being misleading at best because I had been convinced through disinformation that it was the truth and therefore needed spread. I therefore tend to be cognizant of when others appear to be doing the same, seeing in them the same patterns I expressed.
In other words: just because it ain't violating the HN community guidelines doesn't mean it ain't propaganda.
Good question. I don't know if there are any objective criteria, given that the difference between a propaganda campaign and a more benign information campaign is often pretty blurry and subjective.
I think the best bet is to call out (or at least note) the common patterns as they pop up. For example, I know you happen to hold a dim view of accusing others of "whataboutism", but that does happen to be a very common form of modern-day organically-spreading propaganda ("Who are you to say my country does evil things when your country does evil things, too?", says the accidental propagandist, forgetting that two wrongs don't make a right and that one country doing evil things does not excuse another country from doing evil things), and it's important to be able to identify that for what it is. Granted, sometimes that line of thinking is often valuable in the reverse (i.e. "I don't think it's right that your country is doing this evil thing, so I shouldn't be okay with my country doing a similar evil thing."), but it doesn't seem like those sorts of comparisons are typically done with that sort of self-awareness or good-faith desire to understand the other side of the debate.
"Accidental propaganda" is an oxymoron. What's the line between that and just being wrong or disagreeing? It isn't bad arguments; people are even more likely to call 'propaganda' (or astroturfing, shilling, etc.) against good arguments, because good arguments one dislikes are even more activating than bad arguments one dislikes.
The problem is that there are two different phenomena surrounding those words. The first is real abuse; the second is people labeling comments they dislike as abuse because they can't imagine anyone could hold them in good faith. As far as we can tell, the second problem is much more widespread than the first.
\end{jest}
More seriously...
The thing about propaganda is that once someone starts believing it, that someone can potentially (and often does) spread it organically. Hacker News can inadvertently be a hotbed for propaganda spreading of all sorts without even a single bot or paid poster/commenter. I know I've fallen victim to that before, parroting something that ended up being misleading at best because I had been convinced through disinformation that it was the truth and therefore needed spread. I therefore tend to be cognizant of when others appear to be doing the same, seeing in them the same patterns I expressed.
In other words: just because it ain't violating the HN community guidelines doesn't mean it ain't propaganda.