A deep learning AI system has uncovered a relationship between the human face and Dunning-Kruger. Of particular interest was that by far the most significant correlation was one where people are smiling. The correlation turned out to be particularly strong when the research was restricted to a limited number of familiar public figures who often smile in public situations.
This new research indicates that for some people in some situations, a smile does indeed suggest that the person behind the smile grossly overestimates their own ability. I’m not sure how reliable it is, but the findings are certainly interesting.