Hello all,
I registered to tell about my experience with a peculiar double glazed window, that does exactly the same trick of triplicating bright lights, unlike any other window I've seen. I believe it actually triplicates (or more) the whole image, but only very bright lights get a visible reflection.
This picture was taken through the window at a nearly normal incidence angle. Unfortunately I could not take a picture at sunrise or sunset, as the (hotel) window was facing a hill. However I believe the effect is exactly the same. The light is a street light, there are two lens flares, the blue and green lights that are irrelevant to this discussion. This window is a recent model, and has curious properties. When the light is seen through the left part of the window pane, the reflections appear on the left. When the light is is seen through the right part of the window pane, the reflections appear on the right. In between, it is possible to set the distance between reflections to any value just by changing the point of view.
This all points at something uncommon in the glass, either not perfectly parallel or variable width.