Oh, I'm glad my ramblings weren't too annoying. I am a language nerd and I love seeing how things translate into other languages. I was just reading somewhere that in Germany, they translated the nickname that Moriarty gives to Mycroft (Iceman) as the literal eissman. Which is what they call the man who sells ice cream from a truck over there. :D

I see what you're saying and I think you're right. Sherlock is special to Moriarty, so he gets respect. I do think it would be equally in character for Moriarty to use the informal, though. Or swap back and forth. Because he's sooooo changeable! :p