This is a good topic. Our detachment just painted and velcroed our helmets but a couple of us had velcro sewn onto our covers. Last deployment we painted our helmets and never wore a cover. I didn't find anything wrong with it nor was I targeted (that I know of) for standing out or being shiny.
I see the covers being used for snipers, recon, etc...but a patrol of 8-15 dudes in the mtns of a-stan...or even in a village or whatever, helmet covers? really?