How "Anal" Are You With Respect to Runs in Paint?

I'd sand and repaint, that would bug me and I wouldn't let it slide. Just because you can't see something doesn't mean it isn't there.

I have done "body work" on oil pans before because they shouldn't have any dents and then painted them with the same process you would paint the car with.

I always primer engine parts, never just spray engine paint straight on because the color will fade faster than over primer.

I'd absolutely re do that pan