Long ago I paid an elderly gentleman to polish a windshield to remove some sand pits and a wiper scratch. He used a high speed buffer with diamond compound.
End result was a wavy glass that would nearly make one sea sick and a 3/4 inch wide trail of water left by the wiper blade where the scratch was.
Triple 0 (.000) steel works wonders on little scratches in glass. If you cant find it anywhere else you can order it online from Harbor Frieght. ITs around $10 for a 50' roll I believe.