The DKE means people rate themselves closer to average for both those below average and above average. But people below average still think they are below those at the top, just not by the amount they think.
A glance at the graph above should explain everything. Though many assume the slope of the "perception graph" is monotonically negative, the slope is actually positive.
Ah, so everyone is pulled toward the average of what people think, not the average of what people are. My reading nerfhammer as saying the latter is, I think, what is responsible for my unease with his characterization.
Not really here or there, but my assumption from what I'd read on the effect was "not monotonically positive", not "monotonically negative" (which would be more surprising).
But my point, reinforced by the numbers I gave, is that there is overlap in the distributions between "how good I think I am" for those actually at the bottom and those actually at the top. There may well be other cognitive biases at play.