Mostly useful when you are against someone, be it sports,war,politics,debates,even arguments. It kinda changes the flow sometimes. An example can be like a simple gesture while arguing can change the flow
It is. It isn't as strong as depicted in stories, but killing intent can make a person very uncomfortable to the point of them breaking into a sweat or even running away. That depends on whether you consider psychology a pseudoscience. The study of body language is studied in psychology and there have been studies that show that people do read body language and what reaction certain stances, postures, and facial expressions incite in a person.
No offense to this guy, but every time I see someone with their arms open like that it immediately triggers my "enemy" category.
You mean that unnerving sensation of having someone likely staring at you with malicious intent which in result causes your pores to open and produce cold sweat as the feeling of something tingling yet piercing is concentrated on your nape? Paranoia at most cases but on rare occasions, said icy touch saves your life from danger in the next seconds or minutes.