I know that if I scratch 4130 I set up a stress riser. I also know
that I can polish out the scratch.

Reading about welding, I see the warning not to file a weld, but under
at least one circumstance, I don't see the problem.

For example, I fill in a hole I'd previously drilled in a tube. The
filler material sticks up above the tube surface. Why can't I file the
material down, followed by polishing out any scratches? - Mike