Haven't read much further in Riffaterre yet. But this morning his framework seems both too narrow & yet close to something... I've always been interested in the differences between prose & poetry.
Of course their regions overlap... yet generally prose (fiction) creates a "scene", a world, a time - and the narrator hides behind a curtain... whereas poetry emphasizes the presence of a speaker and the time of Now... not so much a mimesis of reality as the actuality of a speaking person, edging or counterbalancing the autonomous quality of the art werke...
Pushkin famously addressed poets as "Sons of Harmony". The poet brings music & measure to the various & contrary discourses of the social world. The poet stands in the middle of it all & transmutes it into a song... this can be dangerous, too (the poet puts him or herself on the line - the prophetic stance).
(The self-consciousness of poetry : first humanity in general created, or came to the consciousness of, language, with which to shape and define reality. Then the poet came along, to bring self-consciousness (reflective awareness) to the shaping of language itself. The word turns on a pivot - revolves there, motionless. Poets and prose writers both do this - but in very different ways.)
Such generalities might have consequences for what passes for the canon of style and aesthetic value. Perhaps it comes down to the question : what is this poet - as "speaker" - actually saying? What is the logos within the melos and the phanos?