The introduction of karma on this site wouldn't be a bad idea.
The system would work similarly to how Reddit works. If your comments/posts get upvoted, you gain karma. If they get downvoted, you lose karma. If your karma goes below a certain number, you should be banned temporarily/permanently from posting and commenting. Would help to filter out all the 10 year olds on this site
Duo doesn't even verify email addresses on creation of an account. I can't see them continually tracking IP addresses. I'd like some system to limit who can vote like you have to have completed a tree. Although I suspect some of the downvote fanatics are just tired of reading how do I .... For the two hundredth time
While Duolingo should keep an eye on accounts posting lots of downvoted comments, a Reddit-like karma is a bad idea, especially if viewable by someone else that the admins.
On Reddit, collecting karma has become an addiction for some, leading to people fishing for easy karma with low-effort content. Duolingo forums are already full of fluff, imagine what would happen if it also gave people imaginary points.