Move funds from earliest known blocks to another, newly-generated address or any other address. That's the simplest and easiest way. Signed message also works, but CSW and co found some loopholes which makes their signed message appear legitimate.
Then again, the real satoshi would probably not try to make his/her identity known, and would just stick hiding and keeping a low profile.
He did extra steps to hide his real identity to remain anonymous. Tin-foil hats on, but I believe he changed his coding style to write Bitcoin, used Windows instead of Unix, or a Unix-like operating system, and he also probably changed his posting style in the forum.