Agreed. Having worked closely with them, I would say such Haskell luminaries as Simon PJ, Lennart Augustsson and Neil Mitchell have not "learned category theor

Agreed. Having worked closely with them, I would say such Haskell luminaries as Simon PJ, Lennart Augustsson and Neil Mitchell have not "learned category theory" (and I don't think I'm being too offensive to them if I state that). In fact the only figure of highest repute in the community who puts much stock in category theory is Edward Kmett.