Why is it "nem" not "ne"? http://www.hungarianreference.com/Misc_Grammar/negatives-nem-ne-sem-se.aspx says that you should use "ne" in the imperative.
Right - that was me with this infinitely witty solution. You see, in case we could have changed the typo, we would have already done it. But we cannot - guys with greater power, higher up in the Duolingo hierarchy could access and edit the database, but they seem to be busy with other courses. I am really sorry.
Please consider this situation temporal like we do - you might see some other unbelievably creative solutions along the tree. The course is in beta, in plain words it is half baked only. I promise to fix several dozens of errors each day and your error reports and suggestions are in general most welcome.
Stressing and voice highness is quite important in Hungarian. For instance, "You are stupid." and "Are you stupid?" consist of the same words in Hungarian "Te hülye vagy" and since there are no sentence marks in real life, intonation tells the other person whether the sentence is a question or a statement. By the way, in this case, intonation in "Te hülye vagy?" should sound like low-low-high-mid. This high-mid, or high-low drop in the end is very usual when asking a yes/no question in Hungarian. If the intonation was simply flat, it sounds like a statement.
Does it mean there in Turkish? According to wiktionary, it doesn't. Also, words by themselves, especially if they sound identical, are generally not a very good indicator of the relatedness of languages. Words are exchanged very easily in a contact situation, completely independently of similarities in grammar, etc. Turkish and Hungarian grammar is similar in some respects, yes, but the commonalities in the vocabulary point to later contacts rather than an old relation between the languages.
Yes - it seems that when a course is in beta then we can only correct the answers, but not the original questions or exercises - we are very sorry about this.
I'd suggest that you just disregard this very sentence and swim with the stream by accepting what Duo says here. I won't kill you but you can advance to other sentences.
If you want to help us then please do not even report it. Thank you and good luck with the others!