Suggestion: user added vocabulary words
I'd like to suggest adding a feature to the vocabulary section.
It would be great if we could add words we learned in the immersion section to our vocabulary list. If it would cause a problem with your algorithms, then perhaps the user added words could be marked differently, or be in a different section.
Perhaps it could even be possible to add phrases we translate, which could then be part of our skill tree, or of a separate skill tree. That would make duolingo a much more powerful learning tool.
Or rather, users could submit new words/sentences/lessons which could be approved by duolingo staff for the rest of the community to use to ensure high quality stuff.
I see what you mean. I like that idea, but I hope it wouldn't turn into something that would require too much duolingo staff time.
I was thinking along the lines of private vocabulary lists not monitored by staff, but now that you mention it, private lists could also be a tool for duolingo. If certain words or phrases appeared x number of times in private lists, then duolingo might want to consider a new module on that subject.