P.S. Jeff replies in comments:
It sounds like we’ve converged. They acknowledge MRP performance is significantly better on average than reported in their new paper in PA and yet performance variation in terms of correlation to “truth” remains higher than some might have thought.
Cool. I hope this sort of blog exchange can be a model of scientific discussion. Instead of a paper just sitting there by itself, it can be openly explored. Ideally, the published paper would include a link to these discussions of Highton, Buttice, Lax, Phillips, and Ghitza, so that readers would automatically get all this information.