It's nice to see the science of social cues get further research. These studies are important if you want to find out why people do the things they do. Ariely spoke about his very concept when it came to financially toxic decisions that lead up to the the 2007 recession. When a peer makes a bad decision and is not punished, in some cases is rewarded, then others take that cue to do similar or the same things. On comment threads it's the same situation. A few people make a comment that is just trolling (aka. you mad bro?) and it blows up. By the above logic, trolls should be banned on forums or punished in some way. They do it here on the escapist and you can even see they were punished, how long for, and for comments on what thread. It's an awesome thing they do.
Now if science could determine a way to teach people what trolling is, that is a real trick. You see, by disagreeing or having a different idea than other people, you are not trolling. People will say your trolling. I once used an analogy in one of my debates and the person responded with something like, "what kind of troll logic is that", when I was in fact not trolling.
I don't completely agree with the Theory of Motivated Reasoning. It's honestly just far too simple to explain complex human interactions. I also feel that if you were to make a list of what motivates the things people say to each other in a social situation, it would have to be much larger and rationality would have to be way down the list. If there is one thing most complex psychological version of various sciences (economics, sociology) have pointed out since Kahneman and Tverski's works that started in the 1960's, people are not rational. That is a strange sentence, but people are not rational creatures. We are capable of rationality. We are also capable of persistence hunting. Neither of which is done by everyone. Though it has a happy far step from on of the other theories that floats around, that would the cost benefit model. That one is completely off base in regards to what motivates people to do anything.