Until today the word "duplicate" was clear to me, or so I thought, but I have just been confronted with the following situation: there is a question A from 2011 (with an accepted answer) and one other, B, from 2015, that asks the same thing (again, with an accepted answer). User U marks question A as a duplicate (!), starting the voting process, claiming that the usual meaning of "duplicate" should not matter and that the question with less (or poorer) answers should be considered the duplicate of the other and thus closed, irrespective of their chronological order. Is this the correct decision?

For reference:

A: What's the name for the property of a function $f$ that means $f(f(x))=x$?

B: Functions that are their own inversion.

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    $\begingroup$ To recap what I said in the linked thread, I consider that if two identical questions have been asked and received answers, the better one (including the quality of the answers) should be the duplicate target regardless of the date on both questions. In this case it's pretty much clear-cut which Q&A is more useful to a long-term repository of knowledge. $\endgroup$ – Najib Idrissi Aug 31 '15 at 12:43
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    $\begingroup$ MSE is not a place to establish priority. Duplicates are not saying that someone had asked the question before, as much as they are for saying "There is already a good answer elsewhere on the site". I'd factor the quality and quantity of the answers, then the quality of the question, then the timeline when considering a duplicate. Well, at least under ideal conditions. $\endgroup$ – Asaf Karagila Mod Aug 31 '15 at 12:47
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    $\begingroup$ You can find a few related discussions on meta: What to do with a newer post and a related, older, less thorough post?, Topics declared as duplicates in which order?, Original post marked as duplicate (Should some of those be closed as duplicates?) $\endgroup$ – Martin Sleziak Aug 31 '15 at 12:49
  • $\begingroup$ If your post is intended as a discussion of the situation in the questions you linked, you should use (specific-question) tag. But I assume that the linked questions serve merely as an example and you wish to discuss the more general issue. (In which case that tag does not belong here. However, it does not hurt to clarify this.) $\endgroup$ – Martin Sleziak Aug 31 '15 at 12:52
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    $\begingroup$ @MartinSleziak: Your last comment gets it right, I am interested in the general situation, the links serve only to give a concrete illustration of the problem. $\endgroup$ – Alex M. Aug 31 '15 at 12:54
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    $\begingroup$ @Martin's links above eventually leads to this: "If the new question is a better question or has better answers, then vote to close the old one as a duplicate of the new one." I think it can pretty much be considered official policy. $\endgroup$ – Najib Idrissi Aug 31 '15 at 12:57
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    $\begingroup$ @NajibIdrissi: Agreed, this seems to be the general policy. I wasn't aware of it. $\endgroup$ – Alex M. Aug 31 '15 at 12:58
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    $\begingroup$ My gut instinct is to: 1) always favor the older version, 2) close (preferrably also delete) the new one as a "punishment" to the lazy asker and the equally lazy answerers who should know to search. If the newer edition has exceptional answers, then 3) merging (if possible) the answers to the newer version to the older. Luckily my diamond prevents me from acting on all my whims, for this would clearly be a suboptimal approach. I do want to emphasize that vote count cannot be used to reliably gauge the quality of the two versions (or answers to them). $\endgroup$ – Jyrki Lahtonen Aug 31 '15 at 13:02
  • $\begingroup$ Interesting points here. FWIW I starred this thread and try to learn from it. I have just seen too many inferior answers to newer duplicates get more upvotes than IMO better answers to the "original". The fact that voters don't even seem to look at the older version rubs me the wrong way. But this is also a very clear case of selective memory or bias from my side. $\endgroup$ – Jyrki Lahtonen Aug 31 '15 at 13:19
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    $\begingroup$ I am not sure what your point is to begin with. A meaning of "duplicate" is "One of two or more identical things" giving as example "books may be disposed of if they are duplicates" (from Oxford Dict., mentioned first). There is no inherent notion of original or older there. It is the case that sometimes one means by "duplicate" a copy or replica of an original, but this is not the sole meaning. $\endgroup$ – quid Mod Aug 31 '15 at 13:44
  • $\begingroup$ Wouldn't it be the ironically correct thing to close the older meta thread as a duplicate of this one? :-D $\endgroup$ – Asaf Karagila Mod Aug 31 '15 at 14:42
  • $\begingroup$ @Asaf This (the new thread) doesn't have an answer, so it's not even possible for normal users AFAIK. $\endgroup$ – Najib Idrissi Aug 31 '15 at 14:45
  • $\begingroup$ @Najib: Sure, but the right thing to do would have been to post a really good answer, then close the old one as a duplicate of this one. :-) $\endgroup$ – Asaf Karagila Mod Aug 31 '15 at 14:46
  • $\begingroup$ @Asaf: maybe give a couple of answers to discussions really quick and with the then received discussion gold-badge you then could make this a reality almost singlehandedly. $\endgroup$ – quid Mod Aug 31 '15 at 15:03
  • $\begingroup$ @quid: Good idea. But I think that posting 30 answers would be a bit excessive just for this. :-P $\endgroup$ – Asaf Karagila Mod Aug 31 '15 at 15:15