[SD987]

Conventional wisdom says that if the scratch is deep enough to catch the edge of a fingernail, then it's too deep to remove.

I know the 987 has water repellent coating on the side-windows which would not respond well to any sort of buffing, and though I don't think this is applied to the windshield, it may have some other sort of coating applied during manufacturing.

If you're going to try a toothpaste, make sure it's a paste not a gel, although this technique is more applicable to small light scratches, such as those on the face of a wrist-watch. I don't think it would work with auto-glass, on a scratch big enough to notice, but at least your windshield will smell and taste fresh !