Thanks for the heads-up – I have changed the image to avoid further confusion.

(“Bayesian Regret” is not a term I actually used in the above post – it is simply in the title of the graph that was taken from Poundstone’s book, which is so titled because it is referencing Smith’s work.)

Since this misnomer is nonetheless in use, I would suggest that rather than leaving the Bayesian Regret Wikipedia article with no reference at all to this usage, it might be better to link to the article about the actual term that is used:
https://en.wikipedia.org/wiki/Social_utility_efficiency
Something along the lines of “The term Bayesian Regret has been used to refer to the concept of average probabilistic regret in Social Choice Theory, however this is something of a misnomer as it has little to do with updating priors. [[Social Utility Efficiency]] is the preferred term.”

I note that this article is linked in the “See also” section, but without context. This might not be sufficiently obvious or helpful for people looking into the term having read Poundstone’s book or Smith’s papers. It would be good for people to be able to easily find out the actual term that is in use, rather than hitting what looks like a dead end.