The C++ coding style is also very much the way a Windows developer would write C++ code. Not the way a Unix-y C++ developer writing on Windows would write.
I always figured based on the code and the emails that it was an older Japanese developer. I've emailed 100s of them over the years and they do all typically write similar in English, they mix a lot of UK/US-ism, and often their English is really good, like I wouldn't know they weren't a native English-speaker until I just caught on to how they wrote. (Speaking is an entirely different issue, many of them cannot speak English in person very well or make obvious grammatical mistakes they don't make when typing.)
Coding is quite subjective. When I examined the early bitcoin code (the one Satoshi wrote and shared). The C++ code looked pretty sloppy and amateur-ish.
The comments were odd and not standardized (randomly using four //// sometimes, etc). The use of 4-6 random new lines between sections of code was awkward. The way the code was organized, folders named, etc.
The code itself was a mix of hungarian-isms. It felt very academic-y to me... like someone that did most of their coding in university as a teacher or phd candidate (little real-world coding).
There's a podcast (name slips my mind...) where the host asked Bram Cohen if he thought Len was Satoshi and he doesn't outright say yes... To paraphrase, he basically answered, "I can't say for sure. It seemed like he (Len) lacked the C++ knowledge.. but his programming got a lot better since I last seen it... so I don't know. It seems to be the most likely scenario would be Len doing the brain work and someone like Hal doing the coding."
But, isn't that sorta what happened? Satoshi had 169 commits and Hal basically took over and cleaned everything up. Satoshi didn't do that much coding, and the coding he did do was done over 1.5-2 years (as he stated in the cypherpunk mailing list).
I always figured based on the code and the emails that it was an older Japanese developer. I've emailed 100s of them over the years and they do all typically write similar in English, they mix a lot of UK/US-ism, and often their English is really good, like I wouldn't know they weren't a native English-speaker until I just caught on to how they wrote. (Speaking is an entirely different issue, many of them cannot speak English in person very well or make obvious grammatical mistakes they don't make when typing.)
Windows is also very pervasive among developers.