Allow users the ability to have open discussions on practices with the ability to upvote comments that add value.
Starting to work on designs now.
@Colin Pace, Are you guys sharing some of your progress via Medium or similar? Would be interesting to follow.
If you mean something like a comments section bellow every lesson, it should be strictly supervised (like Stackexchange's), or we'll end up with something like Duolingo's: Lots of duplicate/spam comments, no ordering based on votes (as I remember) and really hard to determine which user is giving real and correct info.