It is important to remember that these discussion forums are for users of the course, so when you say "you guys" you are addressing other learners. When you say that English spellings are not accepted, do you mean British English? I am British, and always use spellings like colour, grey, and as here, favourite. I have never had one marked wrong. Even British words, like "railway", "petrol", "head teacher" and "shop" are usually accepted too. Perhaps you had something else wrong that you didn't notice, which caused your answer to be marked wrong. What did you put? By the way, the reason for the American flag is that Duolingo is based in the United States.