Do you have evidence besides the username and the programming skill that it's Norvig?

Yes, I have exchanged emails with Norvig about it. But it didn't even occur to me to doubt his authorship, because the style is so similar to his Sudoku solver.

Also, could you tell me your Euler username so I could look for your solutions (provided that you actually post there)?

My username is cousin_it but I never post there.

At first I didn't examine his code deeply, but its conciseness inspired me to create a 12-line semi-obfuscated Python solution. I posted a clarified version of that in the thread.

Woah. If you enjoy crafting your code into such puzzles, check out call/cc in any language that supports it, e.g. Ruby which is really similar to Python. It will help you increase the amount of havoc per line :-)