I could post "splendid" once in a while, but that doesn't make me based in Britain.
A splendid few z and s switches are easy. A bloody stereotypical word here is all that's required to confuse origins.
The majority of his language was technical and specific to the field, which have fewer American/British/Aus/Intl splits.
In the end, there isn't enough there. Most word-grams that I look at hint less American and more British.
Every person's language evolves very mildly over time, and they would be less likely to stick to a persona during the hours they are most tired.
If he had talked more about other aspects of life, there would have been other hints.
I know
nullius has always loved his privacy, up to the point that he tries to post around the clock to hide his time zone. Does his writing style really say anything useful about his whereabouts? I doubt it. Same for Satoshi.
The writing style doesn't say anything, especially because one can move from locations.
If you were to look at any internet forum, you would find that any user don't post as much at their 2am (except for people who work night-shifts, which is very rare to stay consistent).
Satoshi's daily posting patterns put him at about Hal Finney's location (Arizona). (Not to mention that Satoshi disappeared at about the same time that Hal had to quit working due to ALS..)
It is unfortunately very difficult to hide your general location, without scripting delayed responses, and very few people have that ability and are so committed to privacy to consider that.