I remember very well that my first impression upon sitting in a brand new '79 240D was dismay at the firmness of the seat. I had expected a comfort befitting the price of the car and found the front seats nearly as hard as a waiting room chair in a government office. It took a long drive to come to appreciate that firmness's benefit.
It's amazing that such a seat could go as soft and springy as these do, almost without being noticed doing it.