Overprint warning: Please fix this, Adobe
When you have a white element, and you assign that to overprint, you get a dialog box telling you that's not a good idea. However, if you have a black element that is set to overprint, and you change that to white, you don't get a warning (a tiny yellow alert icon appears in the Attributes window, but you don't see it if that window's not open). The user creates the same exact horrible situation in both scenarios, but the second scenario doesn't trigger a warning.
I deal with a lot of logo files that I haven't created, and I need to change some of those to reverse occasionally, usually at a fast pace. If something doesn't print, I get to eat that.