Has Curb Your Enthusiasm softened with age? In some ways, not at all. There is a scene in the opening episode of the new, 12th and supposedly final season in which Larry David is talking to a boring party guest and simply repeats her words in a silly voice at maximum volume. That woman is not seen again. As the sitcom misadventures of the Seinfeld co-creator’s alter ego have progressed, however, Curb has smoothed some of its edge. The addition a few years ago of the phenomenal JB Smoove as Leon, Larry’s priapic freeloader of a lodger, has given the...