I care about whether a comma appears between the "Oh" and the "shit" in "Oh, shit" or "Oh shit." If a character uses that expression twice in rapid succession in the same paragraph, but one instance has a comma and the other doesn't, I can't be at peace until I know which the author intended. Or, at least, which the author allowed to go to press when the story was first published.
This is the kind of thing that keeps me up at one in the morning.
Apparently I'm doing the work I was meant to do in the world.