Among the brand-name French theorists of the mid-20th century, Roland Barthes was the fun one. (Foucault was the tough one, Derrida was the dreamy one, Lacan was the mysterious one — I like to imagine them sometimes as a black-turtlenecked, clove-smoking boy band called Hors de Texte, with the hit album “Discipline ’n’ Punish.”)