The first one is about "encouraging" people to leave comments on downvotes and is marked as status-completed. The second one is about "mandatory" comments on downvotes and is speaking of a feature which does not exist.
I think the first question has a purpose and fulfilled it. But the second one has got another purpose which is not yet fulfilled.
What do you think about this duplicate closure?
Put in the clothes of the guy who sees its answer closed for duplication. He checks and sees that the "duplicate" question was speaking of "suggesting" while he was speaking of "mandatory". It would be better to close the question for the real reason: "community has had that discussion, in depth, came to a conclusion, did that several times, and has settled on a definitive conclusion."