This discussion is petering out, which is a shame, not only because Jolly Roger made an idiot of himself trying to discuss poetry again but because Nameless Wag has come up with an idea that deserves a bit of work. He asks, "How many literary coincidences constitute 'too many'?"
What is needed is a unit of standardised measurement for the literary coincidence. We could call it the Vere. You could isolate a coincidence, measure it against the standardised norm, then give it a value, say 25 milliVeres for a small positive coincidence in favour of the author, -25 milliVeres if it casts a hint of shadow.
Then you could meaningfully add them all up. A score higher than -5 gigaVeres would mean you can strip an author of all credit for his work and assign it to another higher scoring candidate.
Will, of course, would be starting out with 50 teraVeres.