I guess I get now how it would be if it was your own language ;). I don't care much either way. But think (in normal quizzes) both ways should be accepted and anybody who is bitching about that is being childish. Both are a current and valid way of spelling things.
It did give me insecurity issues when I was younger, always so confused if it was center or centre or meter or metre letter or lettre, ow wait... :P