Discussion at the time: https://www.reddit.com/r/Bitcoin/comments/1zrshb/real_satosh...

The consensus is that it was not from the real Satoshi.

In fact the reaction to that forum post are the same as the reaction to CSW's claims: Sign it or it's worthless.

Good point. But on a second thought - signing it might have been in violation of whatever secrecy requirement, possibly a crime, under this theory we will never ever see anything signed from Satoshi.