It's held on by one bolt, and will scratch up the paint underneath it. It also spoils the look of the front of the car.
You'd probably be a lot better off making something on your own. I'm positive that you could do better than Honda did, even if you're just taking a piece of sheet metal, clamping it in a doorframe and bending it to shape.
I have had three Honda Insights and each one has had a different way of attaching the front registration plate. One simply had the plate kinked in the middle and attached to the bumper, the second had a raised black plastic mould - long & straight, the third is also raised plastic but square in shape.
Take your pick! E-mail me if you would like pictures.
I don't much care for the front license plate either. Luckily my state does not require them. The 2000 Insight I briefly had had holes drilled in to the front bumper for a license plate! Quite honestly I'd personally try and get away without the front plate if my state required them.
One thing I saw I did like was one owner fabricated a way to just put his plate in the front grille of his insight in front of the little plastic fins. I like this a lot more than the Honda plastic bracket.