Scratched glass is permanent. I have a few scratches in my show tank also, its painful, but like others said after awhile you just see the fish. Although I guess I should be grateful I have acrylic, where I could buff it out if it got to bad.
Although I'm not sure of the process. I do know that glass can be buffed. I am a licensed Mass stare vehicle inspector and more than once when I failed a vehicle for windshield wiper scratches the owner buffed them out. Like I said I have never done it or actually seen the process . But I do know that it can be done.