One quart in 1,500 miles is not a problem except for the hassle of keeping it filled. If the consumption gets below the 600 mile level mentioned, then you will begin plugging up the cat and fouling spark plugs.
One of the beauties of a diesel is that there is no harm from excessive oil consumption except the expense and hassle of keeping it filled. There are no spark plugs to foul and since oil is fuel in a diesel, there is no harm. You can continue to drive a diesel as long as you can carry enough oil with you to get where you're going.