The OEM shield is marked Lexum in the plastic in the lower right corner. I believe Lexum is a coating. On the instruction sheet for Meguires Plastx, a product to remove the haze and yellowing from plastic headlamps and the likes, it actually says "not for use on m/c windscreens."
Yes the stock windshield has a thin coating on it, I don’t know what it’s called but I have seen windshields that owners over polished probably with a polish that was slightly abrasive and actually wore spots through that coating. Once you wear through that coating in my opinion the windshield is pretty much ruined.
Guidance of wash with water only, a mix of peroxide helps soften the bugs and should be safe. I've not had a problem. Also small aircraft pilots have plexiglass and lexan windshields also and swear by pledge furniture polish to help water shed, I've used it for a couple years and it seems harmless albeit short lived. I use pledge on long buggy trips on all my forward facing plastics.
OEM windshields are made from Lexan or what they call MR10 which is a mar resistant polycarbonate. This coating is not very abrasive but it is formable which is what OEM manufactures want so they can use pre-coated material and form it without causing any harm to the coating.