Consider this question.
I went to close it as a duplicate of these two [emacs]-tagged questions on StackOverflow:
I was informed that questions are not duplicates if they are not on this same site.
Is that the right policy? So we encourage users to duplicate the 8 zillion [emacs]-tagged questions on SO and SuperUser and...? Why is this good?
This post on this meta site tells us: "During the private beta: if you see an existing question which has not been satisfactorily answered and that interests you personally, then feel free to re-ask it here."
Maybe that's good. Maybe not. (FWIW, I see no good reason given in that post for such a policy.)
But suppose it is good. What about questions elsewhere that have good answers there? The above policy specifically calls out the criterion that the question elsewhere not have a satisfactory answer, so presumably duplicate questions with satisfactory answers (perhaps even accepted) should not be duplicated here.
And yet they are not to be closed as duplicates. Does this make sense?
[Update 2017-05-26] Here's another one. Surely there ought to be some way to consolidate such questions - move them here or be able to close duplicates here.
[Update 2019-01-11] FWIW - For cases where the same person poses the same question here and on SO (typically at about the same time), I've been entering a comment for each question, asking that they post to only one of the sites: pick one and please delete the other. I think 100% have then done that. That helps to (1) concentrate answers in one location and (2) nip a bad habit in the bud.