The Dunning-Kruger effect is probably just from bimodal skill distributions

This is so speculative. I think the first step in determining why some people believe they are much more competent than they really are would be to interview them on how they came to believe it.

I think the fact that the author thinks this is unnecessary and that he can determine the cause of this phenomenon without this sort of empirical research indicates he believes he is better at understanding how one goes about determining human psychology than he really is.

"probably" according to what? Just producing a possible decomposition of a graph and arbitrarily assigning meaning to the components is rationalization, not empirical inquiry.

Isn't the Dunning-Kruger effect considered an over-simplification and not true in general?

Good article. I particularly like the line, "early exposure to experts reduces delusional confidence", which is very true. It helps prevent a flawed Occam’s razor mindset, where people mistake the simplest visible explanation for the correct one.

Though probably not the best title as more about "Mount Stupid", than Dunning-Kruger.

Why are you using the straw man graph for your curve you're addressing?

Where's the top quartile drop relative to measured performance?

D-K effect wasn't only around low competence overestimation but regression to the ~80% mean on both sides.