Questions that are duplicates and triplicates are still asked, even though the automatic "Related Questions" list that appears must be showing them!
These re-asked questions still get upvotes even after a question has been closed as a duplicate. To further discourage the questions, perhaps prevent upvotes to them after they've been closed? Or transfer the upvotes to the master (canonical or original)?
Also, this might help meta question Please charge rep for questions after threshold.