Cannot close as duplicate questions that were posed on StackOverflow?

Question

Consider this question.

I went to close it as a duplicate of these two [emacs]-tagged questions on StackOverflow:

• https://stackoverflow.com/q/14764130/729907
• https://stackoverflow.com/q/22479140/729907

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?

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[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.

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[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.

Answer 1

Why would you want to do that? We bring together individual communities to share their own unique brand of expertise, and you should take every opportunity show off that prowess to build on your own merits wherever possible. (Otherwise, why did we create this site?)

The folks here will work hard to curate a complete collection of knowledge, so when someone comes to your door looking for help, the last thing you should do is send them ELSEWHERE to find that information.

Of course, I wouldn't just blithely start duplicating content from elsewhere — from Stack Overflow or anywhere else. That does not make the Internet better or make a strong case for this site. But unless a question is off topic for this site, when someone comes to you looking for help, you should help them… not send them elsewhere.

Respect the community – your own, and others’

Answer 2

I believe one of the intentions of the Stack Exchange network is (ideally) to provide, for any given (relevant) question, a single page which collects the best answers to that question.

The idea that we should intentionally dilute the good answers by splitting them amongst multiple locations (and across multiple sites!) would seem to be entirely contrary to the aims of the network.

There's absolutely no harm in having a local Q&A which says "actually, this question has a pretty definitive answer over there". That retains all of the benefits of having the question answered locally, without introducing the negative side-effect of splitting the answers to a single question across multiple different locations.

As Drew points out, Emacs questions have long been answered on StackOverflow (especially) and SuperUser (to a lesser extent). We already know that those Q&As are not going to migrated, so it is in the best interests of the end users for us to direct people to any existing good answers on the network, when duplicates occur.