In our modern age, even tiny scratches can be viewed as defects, but we're spoiled. Fifty years ago, tool marks weren't uncommon with blades and tools produced by hand. And yes, it's possible your knife was mangled by its previous owner. Perhaps he couldn't get it as sharp as he'd wanted and gave up. I know some people who get a little wear on their knife and they get rid of it. Seems they want it to always be pristine.
I've got another friend, though, who's a photographer. The first thing he does when he gets a new camera is to take a nail and scratch it up. In other words, he mars it on purpose. His rationale is that it keeps people from stealing it. He used to have a lot of cameras stolen when he'd put them down. Although what he did really rubbed me the wrong way, I have to say it worked. He could put one of those cameras down and no one would even try to steal it. He used his camera as a tool and didn't care a whit for cosmetic appeal.
It's pretty easy to get a good deal on a perfectly functional knife that's seen some hard use. Me, I'm into the cosmetic appeal of knives, guns, cameras, etc. I'd never mar any of them but, on the other hand, I do use my knives. I try to keep them nice, but I don't obsess over it. At least very much. I will use polish to keep them looking nice and would likely apply black paint or ink to streaks in some of my black, or blued, knives.