In general, the ear clips exist as a toggle to allow players to avoid the sex mechanic in battle at certain points. It's somewhat of a meta thing however: narratively, Mezz can't remove the clips because he doesn't know they're there.
Once Mezz has been defeated 3 times, this ability to toggle off the battle sex is removed: you can remove the clips, but it won't do anything. This is by design. As for the sprites, while I try to maintain "common sense" consistency for the most part, I'm not sure it's worth digging through the code for this particular case at this point. I will take a look when I have a chance though, and see if there's a simple way to address it, and to see if I can remember whether this was deliberate for some reason or a genuine oversight. Thanks for reporting though, regardless.