Ah the thread that refuses to die. For those just tuning in, our story so far -- the GSG may or may not have been written by Kate's killer. It may or may not express an anti-Jewish sentiment. The writer himself may or may not have been Jewish. As for what the message means nobody knows and guesses are welcome. Stay tuned for further developments but holding of the breath is not advised.
Very well summed up account of both the facts and the Thread