LOL! I love it when they get all dominant and flare. ;) My oldest guy used to flare at my laptop when I'd work in front of his tank...he'd see his reflection in the black and flare and flare and flare... :)
I agree with some of the others, he might actually be saying hello, or some version thereof. :) If he learns that when he flares he gets food, he may be doing it for food, just like a dog will sit and expect a treat.
All of mine live in divided tanks, and they flare at each other throughout the day, but if one leaves for a hospital tank, the remaining fish gets very depressed and lonely. I know that flaring is a dominance thing...but sometimes I wonder if they're not "play fighting" and interacting through it as well. :) Which could be what your guy is doing with you. :)