Has any consideration been given to a Duolingo based chat?
At the moment I am using HelloTalk on an Android mobile, but finding a Conversation partner at the correct level was difficult. I have found one now, and she is great a correcting my grammar and sentences, and relishes the fact I do it back for her. But it seems to me that if we could "chat" to other Duolingo users who are at the same level but on the opposing language, this could help immensely.
The chat program would scan the words as they are sent, and any "new" words could be highlighted as a different colour, similar to the way it is done in Duolingo lessons.
I think this idea has great potential, and could start off with simple text based chat, and lead on to vocal chat once you reached a required level on Duolingo, this would give incentive to progress in order to chat to people, and gets the user accustomed to hearing the language they are learning.
The world of public education in the United States is quite paranoid about chat...they fear that their young students would be preyed upon by sexual predators. US regulations forbid any app or website operator from collecting any personal information (even email address) from any person under the age of 13. Chat forums, while good, would immediately make Duolingo unsuitable for US-based public schools. Perhaps high schools, but no K-8. Bummer, eh?