I always tell my students to learn new words in French with their article, in order for them to memorize the gender AS they memorize the word. So, in the list of vocabulary for each lesson, it would be helpful to have the nouns with their respective articles, rather than have to click on them to get that information.
It seems as if this suggestion has been made at least a few times a week for as long as I've been using the site (over 10 months now). Duo's response, when given, has always been that they're considering it. At this point, I wish they'd go ahead and do it just so we can stop cluttering up the forum with this suggestion over and over again. The most recent time that this suggestion has received an official response from Duolingo was just two days ago: http://www.duolingo.com/comment/1024713