Recently got Dale DeGroff's Craft of the Cocktail, where he repeatedly advocates flaming the orange peel. They also did this a lot at Sidebar in Silver Spring, the bar that in many ways got me into cocktails. However, Robert Hess never calls for it. It never comes up in The Joy of Mixology. I don't think it's ever called for in the PDT book, or Wondrich's Imbibe.
So, does it really make a difference? Though certainly showy, in theory shouldn't it actually decrease the amount of oils expressed into the drink (since they're getting burned away), and thus lessen the effect of the orange twist in a drink?