Look at some of the other comments on this very thread. Not the top vote-getters, but the ones that must have gotten two or three upvotes apiece. Several of those could easily have been generated by an AI designed to rephrase an already-popular view, perhaps with a pop culture reference or two thrown in to make it seem more authentic. Voila, instant karma, which can then be used in the ways the original presentation suggested to influence who reads what.
It only seems easy until you spend five minutes thinking about it.
Additionally if the AI can beat the turing test then comparing the posts would not be practical. Passing the turing test signifies that it is not possible to distinguish the comments from human comments by looking at the comments alone.
Recognizing the same topics repeated is enough, even if it happens over time. The longer the time between posts, the less effective the campaign. The less cohesive the topic, the less effective the campaign. This already exists somewhat, machine or human is almost irrelevant.
For better or worse, that seems to be an attack vector in a free marketplace of ideas: finding ways to burn the time and energy of your opponent. (See also: "outrage fatigue".)
One of my rules is that, if someone seems to be trying to get me to invest considerably more time or energy than they're investing, I'll only engage if I find the process of researching/writing about a given topic valuable in and of itself.
Some might say we're already half way there. I disagree. Yes, Google or Apple employees might swamp an occasional thread here and there, either openly or covertly, but what I'm talking about would be a whole order of magnitude worse and constant.