Count me IN as one who has this issue
I have 4K or so miles on the car, and have a spot at each side that is worn to the primer already. This is NOT good.
Since people are having different spots where the abrasion occurs, I think the fix is to use a more rigid plastic/fiberglass to make the spoiler out of. It feels just too soft to me. I had noticed this softness before, but didn't think anything of it. Of course this would involve painting said remolded spolier, then removing existing spoiler and touching up or repainting the trunk-lid, and ideally waiting a period of time (for paint and clearcoat to cure) before mounting the new spoiler.
How could something THIS retarded slip through the cracks at Honda? Spoilers are not a new technology. Maybe this particular material us new, which means it should have gone through extensive testing to determine its flex properties. BIG oversight.
I, too, drive mostly freeway speeds, FWIW.