Maybe we need to hash out the data on diffraction in a new thread. For sure, the sweet spot of the lens IMO is about one or two f/stops from wide open, and as it gets down four or five f/stops I become concerned about loss of sharpness as a result of diffraction.
Maybe the resolution of some of the modern lenses with better coatings makes the differences in stopping way down more apparent when we look back forty years to those who were in the f/64 crowd. Interestingly enough I still have a Schneider 90mm f/8 Super Angulon from the 1960's which my guess is would be fairly sharp at f/22, f/32.
So, let us see what everyone has to say on diffraction.