Suggestion: Retrospective translation explanation
So, not a biggie like those neat blindfold translation ideas, but I think it's logical that if you can revert to an old translation, you should be able to explain why, which currently isn't possible.
I think it would also be helpful to have a discussion section incorporated into each article somehow, so that people can share their ideas about the topic and perhaps settle conflicts about translations. Right now, it's not very easy or intuitive to communicate with others who are translating an article.
I hope this idea gets considered. I've loved seeing Duolingo grow and improve since joining about a year ago.