I too think it is down to style of driving but also combined with poor quality of finish. I tend to hook my thumb in that position with my elbow resting on the door (UK Right hand drive) when driving in a relaxed fashion. I think it is then caused by my thumbnail rubbing in that area.

I have to agree as well that it should not be happening in a £50,000+ car. Mine only has 14250 miles on the clock and it just seems to be getting worse.

I've got it booked in this week for checking out an oil leak since it's first oil service in May/June. I'll try to see whether they would replace this then.