these are his first posts yes?

http://sourceforge.net/mailarchive/forum.php?forum_name=bitcoin-list&max_rows=25&style=nested&viewmonth=200901

From reading them he doesn't strike me as Japanese born, the english is way too smooth unless perhaps he had one western parent. I know a lot of Japanese including plenty that have spent decades living and working in the west, all of them give themselves away with a few paragraphs of spoken or written text.

What was his email back then? Satoshi@vi.. viwhat?

also this was news to me but what do I know

"For now, you can just multiply the total blocks by 50.  The Bitcoin network has been running for almost a year now.  The design and coding started in 2007."

the way he writes that sounds very much how you'd write it if you were heading a group, one that only went public one to two years after getting the basics working.

Also given that he spells "realize" and so on with a Z, his style is firmly american english not british english.