As far as I know, Hobie uses the same plastic formulation on all its kayaks. Remember, the Island is simply a modified Adventure. It weighs quite a bit more though, so abrasions will obviously make more of an impression.
Most of the scratches seem to occur right on the keel line. I use a strip of clear packing tape there and let the tape take the brunt of the impact -- easy to change every couple of months.
Hobie's polyethylene is pretty tough though, despite easily being scratched. I saw one that was bitten repeatedly by a shark last year -- the teeth marks just glanced off rather than penetrated -- amazing! I also dropped my Adventure off the back of the roof rack last year while driving off (rather embarrassing). I was sure the boat would be broken -- just got some abrasion at the back of the skeg! I suspect a harder shell would be more brittle and easily fractured.
You can smooth cut marks with a razor blade if desired.