Will a clay-bar remove a ceramic coating?

The clay bar its self should do harm to the ceramic coating, but what's on the clay bar might cause damage.

A clay bar is a sticky brick of plastic which will pick up metal particles, grit and other contaminants, when you rub it over your paintwork. This removes it from the paintwork, but it sticks it to the claybar which you are then rubbing over your paintwork. This will cause light scratches, which is why we use clay bars and similar products at the beginning of our process, before polishing the car.

We would advise against using them as a matter of course as part of your washing routine. If you have any of the problems that clay bars are designed to address, such as industrial fallout, there are other, less aggressive ways of dealing with them.