> It's a 27 step gradient over relatively small change of colour intensity. He's shown a 50 step gradient from WHITE to BLACK. That's not the same thing you are describing. All quantization involves introducing steps -- the question is to determine when those steps are perceptible, and when they are not. Show that 50 steps is too few from 0xFF to 0x00 does not tell us anything about what step size is perceptible from 0x80 to 0x9A.
The article's example is bad, but the problem is real, and it's one I have run into repeatedly in practice; that's why I gave you the $80 to $9A example. Throw a few gradients with that level of stepping on a few translucent layers, and the banding starts to get very noticeable. Dithering helps, mind you.
As a regular gimp user, higher color depth isn't the highest priority thing on my wish list; you can work around the color depth if you have to. It would be nice not to have to work around the problem any more, however.