I consider myself a linguist. I speak Mandarin, Korean, and a Filipino dialect. In addition, I have studied Japanese, Tagalog, Russian, German, and Spanish. This program teaches people to translate literally without any critical thinking about how to say things naturally and contextually right. For example, "Él apareció sin camisa." was translated by most people "He appeared without shirt." Who talks that way. It should be translated less directly as "He arrived shirtless." or "He came shirtless." Another example is "Si ves deportes, es divertido." was translated by most as "If you watch sports, it is fun." In English, that is weird and clunky. It should be translated as "Watching sports is fun." When I translate less literally then it gets marked as wrong even though my translation is better. At the very least there should a way to challenge literal translations that just suck.
They're aware of that issue, and when they reject your translation, there's a "Let us know" link. You'r suggestions are being reviewed by humans and, in my experience, are accepted most of the times. They sure make a candid effort to improve the system and to allow as much natural language as possible.
When pressing the "let us know", you don't even have to explain - they get the question along with your rejected answer. After reviewing your suggestion, they will send you a mail with their resolution. They're on the good side, don't worry... ;-)
I cannot agree with the original comment more strongly. It's infuriating to see people putting their English-language mastery to one side and translating things in totally unnatural ways into their mother tongue. I was told, for example, that '4th November' wasn't the correct translation for 4 de Novembre (not sure if that's spelt right in Spanish!), because everyone had translated it '4 of November'. But nobody would ever, ever say that in English. I think there should be a be exclamation mark in a box pointing out that they want you to translate into good, accurate, natural native-tongue, not weird word-for-word-ese as some people are tempted to.
I'm also not sure that it helps that on the whole I see pretty weird sentence fragments in the 'from the real web' sections, with chunks of blogs, etc., rather than formally written, full sentences.
Sorry to bring this up again, but I too am getting a little fed up with failing tests because of silly sentences that are to be translated literally. I understand that a lot of the seemingly weird sentences serve a grammatical function that is being taught, but what I object to is when I am penalised because I am not literal enough:
Translate: Comment fait-il pour la reduire?
This sentence does not have a literal, word-for-word translation. Instead it would correspond to the English: "What does he do to reduce it?" or How does he reduce it?"
BUT NEVER the offered answer: "How does he make to reduce it?"
I speak French to a high level and am worried that this site, for all its good, is going to put people off because of the amount of gibberish it attempts to teach in its lessons.