While the pop-culture notion of the Dunning-Kruger Effect is "idiots don't know they're idiots," the actual results of the paper were (essentially) that F students thought they were D students, whereas the A students thought they were B students. The argument here seems to be that the original effect is explained as essentially a kind of reversion of the mean argument (people assume themselves to be more average than they are), but I don't entirely buy that--especially since the simulation results they present don't really look like the original Dunning-Kruger results, since the crossover point is in the wrong place, and that's actually kind of significant in the original analysis...