Seriously, it could be anything, even a beanie with a little plastic propeller on top. This is why my “police as predator” analogy holds. Anything that attracts their eye as out of the ordinary will attract their attention.
They are even sensitive to other people’s attention, as well. I had a friend who was doing a citizen ride along with a cop, and he noticed a car ahead with a burned out taillight. The cop noticed that he noticed, so pulled the car over.
He just gave the driver a mild warning, however, and this was also important, because he told my friend that she was a poor woman with some kids, and he didn’t want to give her a ticket she would have a hard time paying. (With the subtle message of “so stop paying attention to things that I will have to do something about.”)
Yeah, they’re human. But they are also predators.
I think what you’re getting at here, is that it’s wise not to be gratuitously strange in such an environment. I’d agree. Not everything legal is wise.