I have a couple of hens that do the same thing when I scratch their ears and they dont have lice or mites. They just like to be scratched there.I think my chicken whose comb gets lighter as the day progresses may have ear mites/lice. She loves to have her ears scratched. She shuts her eye and almost leans into it like a dog would....
The only way to tell if there are ear mites (or other problems) is to gently raise the "ear flap" and look closely inside the ear canal. It should be clean/clear and free of debris; free of anything that looks like ear wax, yellow/green discharge, dirt, black or brown specks looking like ground pepper etc...
The most important place on a chicken to inspect for external parasites is around the vent area where it's warm and moist. There's no need to use a miteacide if you dont see external parasites. Also, inspect roosts at night with a flashlight and see if there any parasites crawling around, they will be very tiny. Let us know if you see anything out of the ordinary.