The point being attempted (obviously unsuccessfully) was that there are more explanations for people participating in a community than you seem to be able to imagine.
Obviously in the presented scenario the silly idea that people are being paid to participate doesn't make sense.
Carrying the concept just a little farther, if there are stock board communities with detractors that aren't being 'paid' because the stock is a standard pinky scam and there are no outside forces willing to pay detractors, then those people have other motives for participating. Even if you are incapable of imagining why they are there, the fact is that they are there. So the issue isn't their motive it is your limited imagination.