i had a similar problem with my old monitor (not that my current one is much newer lol), i found that at certain angles it would magnify the pixels behind giving me red, green and blue lights on the scratch, i found that slightly changing the angle of the monitor would make the magnification "go away". this is the only solution i found that would make the problem bearable.
also, dont try to polish it out; in order to do this with glass it would have to be quite an abrasive action, this would only make the distortion of the scratch become spread over a larger area.