It probably wasn't the real Satoshi that posted the comment on that site.
His @gmx.com email account had been compromised so it's very possible the poster gained access just by issuing a password reset. Some old CMS systems also issue generated passwords sent to your email upon registration, so the password could have been obtained that way as well.
The GMX account password could be reset by knowing the accounts date of birth. The p2p foundation site leaked the date of birth used by the account there.
(the date used was the day of the year that eo6102 made private gold ownership unlawful, and 1975-- when it became lawful again)
His @gmx.com email account had been compromised so it's very possible the poster gained access just by issuing a password reset. Some old CMS systems also issue generated passwords sent to your email upon registration, so the password could have been obtained that way as well.
Further reading: https://bitcointalk.org/index.php?topic=775174.0