In the awards industry, a razor blade is often used to cut and scrape out excess cured adhesive after bonding a glass upright to a base. In doing this, the blade can easily score the glass surface, thus weakening it.
Also, a razor blade is often used to remove mask material, water marks, or surface residue stuck to the glass. However, removing any of these by using a razor blade at an acute angle can and will put a scratch or score on the glass surface.
To avoid causing scratches or score marks always use a razor blade at a very low angle against the glass and use a forward push scraping action. Better still, purchase an inexpensive Scraper Tool like the one shown below from Amazon. It is designed to remove stickers from glass windshields and it is curved at a very low angle to avoid scratching the glass. Use it with a forward pushing motion with your hand parallel to the glass and you will avoid scratching the glass.