Let's compare the D60 to the D30 using this formula:
D30's pixel height to sensor height ratio: 1440 pixels / 14.9mm = 96.6 pixels/mm
We'll be able to use f/22 without concern for visible diffraction because the ratio is less than 100 pixels/mm.
(If you want to see how this was derived, you'll have to work through the math in my original article - at the top of this thread.)
D60's pixel height to sensor heigt ratio: 2048 pixels / 15.1 = 135.6 pixels/mm
This exceeds 100. We won't be able to use f/22 without inducing visible diffraction because the ratio exceeds 100 pixels/mm.