lucy24 - 11:31 pm on Feb 19, 2013 (gmt 0)
it's allowed to redirect to a watermarked image as long as the image size is the same. If you redirect to a smaller size image but with same scale it won't show up. That's a small signal telling you that it's ok to watermark... otherwise why would they allow same size redirection?
If it's the same size, the computer "thinks" that it has met a run-of-the-mill redirect where the image has simply acquired a new URL. If it's a different size, the computer "knows" that there's some hanky-panky going on.