The so-called "idiot scratch" on a USGI pistol is like holster wear in the usual spots on the slide and frame. It is rare to see a pistol that's been used that doesn't have it, which means it's perfectly normal. As a matter of fact I've been told that GI's were often instructed to push the slide stop against the frame first, then slide it up and into the takedown notch as a means of getting the pistol reassembled more easily.

Now a commercial pistol, that's a different matter. The condition of the finish is paramount and any scratch is a bad thing regarding value.