Yes, you want to be very careful when wearing jewelry when you are using your Pen Tablet or Pen Display. Any metal that rubs against the surface of either the Pen Tablet or Pen Display can and will, over time, scratch the surface.
The best practice is to remove any jewelry that will come into contact with the Tablet.
There is no way to fix it once the damage is done, and it is not a manufactured defect.
The image to the right shows a Pen Tablet that the user was wearing a bracelet when drawing.
Over time the bracelet started scratching the surface of the Pen Tablet.
The image to the right shows a scratch that was made on a Pen Display 24 by a large sharp ring.