Getting back to the thread - in your OP you referred to the idea that “...light from an object that was moving away from us at superluminal speed would never reach us.” and “A distant object is moving away, relative to Earth, at superluminal speed...”

You then write “At a given point (say 15 billion l y away....) it emits a photon. This photon should reach Earth 15 billion years later.”

As pointed out by Davies and Gribbin, light emitted by an object that is moving away from us faster than the speed of light never reaches us.

“Clearly we could not observe galaxies that recede faster than light, for their radiation would never reach us.” (111, 'The Matter Myth', Viking, 1991)

It is my understanding that Professors Davies and Gribbin are recognised authors of physics books and articles who would not be prepared to publish something that is not accepted by the scientific community in general ergo I prefer to accept their word as to what takes place.