Can someone explain how he signed the 'Satre' quote WITHOUT having to break SHA256 (finding a collision) ?
It's pretty important, as if he did do that, Bitcoin is broken.
He never used the hash of any Sartre quote (that was just misdirection) - the double hash that he used was simply that used in Satoshi's tx along with the signature that was used in the tx.
(basically he just copied and pasted from the blockchain then put together an elaborate pretense that he had somehow managed to sign something else using a private key known to belong to Satoshi)
You don't know that he didn't. He hasn't yet revealed which portion of the Sartre text he claims hashes to the same hash. That was what I explained and discussed in the thread I created which Gmaxwell has apparently sent to the ether.