Yes, many instances of modern literary criticism come to mind, such as Ben Jonson's commentary on the works of Shakespeare, his friend, producer, and cast membe

Yes, many instances of modern literary criticism come to mind, such as Ben Jonson's commentary on the works of Shakespeare, his friend, producer, and cast member; Cervantes' analysis embedded in Quixote and Sheridan's analysis embedded in Tristram Shandy; Tolstoy's What Is Art; etc. My impression remains that during the period between Poetics and, oh, Canterbury Tales, the great thinkers didn't publish anything about Narrative. Thanks for the Northrop Frye tip!