The creator, Satoshi Nakamoto might be also British, American, Japanese or whoever he wanted. My point is that no one really knew his exact identity or where did he live or where was he born. There's a lot of speculation that might be connected to his identity but up to this point, nobody was able to prove about his whereabouts. The fact that he is already clever enough to create bitcoin means that he's also clever enough to conceal his identity.
You already said it yourself, the evidence you laid is not really concrete. The Russians may have been in the forum since 2010 but that is not proof to say that SN is Russian. My theory why the Russian Board is very active is because not all of them can understand and talk English which is the universal language, they are just all congested in one board.