Seriously? You're going to complain about his English?
Perhaps he's a non-English speaking coder who is expressing admiration and incredulity? What makes you think he's complaining? He goes so far as to explicitly state "no offence".
There's a boundary between playing devil's advocate and taking the piss outright.
When is "no offense" ever attached to a compliment?
Because he is able to not only master his native tongue but also acquire some fluency in English. You people born with English as native language wouldn't know how hard it is to keep switching between 3-4 languages constantly.
Chances are you're better than him at English... and he's better at programming.