Mirror scratching is not about making scratches on a mirror (and not DIY on how to remove them). It is about one of those odd mind-body phenomenon.
You have an itch, so you scratch it. Except sometimes scratching is not a good thing to do (poison ivy, scabs, eczema) because it makes things worse.
There was a study done to test “whether central mechanisms of scratching-induced itch attenuation can be activated by scratching the limb contralateral to the itching limb when the participant is made to visually perceive the non-itching limb as the itching limb by means of mirror images.” In simpler English, try scratching your left elbow if the right elbow itches.
Crazy, right? But it worked! By scratching the non-itching place it seems to have activated a “mirror condition” so that the non-itching place was visually perceived as the itching place.
We have in our brains what are referred to as mirror neurons but this isn’t about that. This particular experiment used a real mirror placed between the participant’s forearms “to create the visual illusion that the participant’s itching (right) forearm was being scratched while in fact the non-itching forearm was scratched”
The mind not only plays trick on us, but we can trick the mind.