Shirow's compliments (as with anyone's) can sometimes come off as overboard... and I admit, it used to creep me out, too. But having gotten to know him as a friend, I can say with 100% certainty that he is being sincere.
And I can understand why he feels the way he does about this picture; it's very striking. I don't know anything about this character, but I'm intrigued enough by this one image of him that I'd like to know more. The "dull" colors, rather than making the picture boring, add an extra element of character to the piece as a whole. It has a whole "I bet you wish you knew why I was sitting here, DON'T you? ... Well..." feeling... but is he going to tell the viewer his story, or tell them to piss off?
I guess all I can say to you, Shirow is... I dunno. Be more discreet with your praise?
Real nice...Your very good with water colours, I never seen anything like that before, i mean i have by you and I love'em. Very nice indeed you really should look into art as a like a career! You're great in it!