I think Duo is trying to teach us Italian the way children learn Italian as a mother tongue - through observation and trial and error. For those who persist with this method it works well. Of course, there is nothing to stop you complimenting what you learn on duo with traditional formal textbook Italian which can also be found free online. And probably duo would commend you for using a variety of approaches. I think Duo works extremely well for some people, especially people like me who enjoy games. Duo has caused me to learn fairly well with enjoyment many hundreds of Italian words I might well not have learned at all. That's a great result!!
I does seem like you have to pick up a lot through context and repetition. The pronoun "si" continues to confuse me, especially when it pops up in a sentence where it doesn't seem to do anything. A formal Italian course would likely explain why it's there, but I don't get that here.
That said, I'm a better Italian speaker for having come here. :-)
I agree with funny. It's a good method of throwing you into the language. The community helps to supplement the teaching and now going back to formal language learning makes it easier.
Here's a TEDx talk by one of the founders of Duolingo that I thought was very interesting: http://www.ted.com/talks/luis_von_ahn_massive_scale_online_collaboration?language=en
I don't know if anyone else has noticed this but Duolingo gives a far more detailed intro to a section on a computer than it does on a phone or tablet. They are not the same levels of information. The computer is a far superior means of learning the information before starting a new section (under the tips section)
I too wonder this. In fact using google translate. Both "He likes his work" and "They like his work" translate to the exact same phrase "gli piace il suo lavoro" - which is essentially this sentence. So I'm not sure why DL doesn't accept They like his work for this answer/translation. I've read through responses so far, but they all still seem to hint that this could be a possible meaning.
In a different question, I put "La sua famiglia gli manca"' but it would only accept "Gli manca la sua famiglia". It seems like 'piace' would use the same construction as 'manca', so I think yours would be ok. I think we need confirmation from someone with a lot better Italian than mine, though! Also, I love your verb Yoda-ize: descriptive,succinct and funny. :)