Simple as it sounds, display the full layer name in the table of contents pane on hover. I tend to leave breadcrumbs for myself and successors in my "scrap" maps and this would be very useful.
@TanuHoque 3.3.1, I do see that now, thanks - I don't get a popup when hovering over a selected layer, though. Also interesting that sometimes they are white on black and other times black on white.
I tested with selected layers and it woks for me too. It is odd that it is not working for you or you are seeing them in reverse color. This would be something that a support analyst can better help you. We'd appreciate it very much if you could call Esri Support and they are in better position to help you in this case. If it turns out to be an issue with the software, we will take a look.