HN is definitely a target for these kind of people. It has gone so far as high level contacts between the bosses of these kind of people and the stewards to sort things out. That doesn't mean that it has stopped nor does it mean there won't be repetitions. Astroturfing, burying, and derailing all happen. The scariest aspect to me is not those that are paid to do this sort of thing, because I can see their motivation but their little helpers in the form of the gullible public. From the above you could probably conclude I'm a cynical old bastard these days and you wouldn't be to far off.
I suspect that any forum with more than a few thousand participants has elements that are trying to actively shape the conversation to serve their goals on it.