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Currently the system detects duplicate answers from the same user and flags them for moderator attention. This is useful, but could be streamlined.

Duplicate answers fall into two main categories:

  1. Spam.

  2. Answers to duplicate questions that haven't been closed yet (or even attracted a single close vote/flag).

In the first case there is absolutely no benefit from having multiple spam posts - except perhaps to confirm that the user is a spammer rather than just misguided.

In the second case the user probably doesn't understand the system so preventing them from posting and telling them to flag the post as a duplicate is educational.

If the user gets this message and then posts a different answer to the same question then this should be flagged as this would indicate they are trying to get round the system in some way.

There are occasions where the same basic answer can apply to different questions, but in those cases the actual answer posted should really be tailored for the specifics of each question and therefore the actual answer won't be identical.

  • I don't get it, if it's a duplicate then that means it's closed and you can't post any answers, right? And if it's not a duplicate then what's wrong with posting an answer...? I feel like I'm missing some context... – Mehrdad Dec 6 '13 at 10:33
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    @Mehrdad - if it's a duplicate and not closed it should be closed as a duplicate rather than being answered. – ChrisF Dec 6 '13 at 10:33
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    And if the person answering it disagrees that it's a duplicate...? – Mehrdad Dec 6 '13 at 10:34
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    @Mehrdad - if exactly the same answer can be applied to two questions then there's a good chance that the questions are duplicate. It's not always true, but the cases where it's not are quite rare. – ChrisF Dec 6 '13 at 10:35
  • I'd suggest it's sufficient to mark as duplicate if a new answer fails a plagiarism test against any answer already given. Such algorithms are well-known; particularly for computer code which work at the token level (assuming you're talking specifically about Stack Overflow). If an answer is blocked in a constructive / diplomatic manner then no offence ought to be taken. – Bathsheba Dec 6 '13 at 10:37
  • I think I must have misunderstood your post, never mind. – Mehrdad Dec 6 '13 at 10:38
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    How would you calculate if answers are duplicated? Or is this calculation in place already? And there is a third reason - different questions with one answer, like famous caching here on meta. – Mołot Dec 6 '13 at 10:47
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    @Mołot - this is already in place. Duplicate answers from the same user are automatically flagged by the system for moderators to deal with. – ChrisF Dec 6 '13 at 10:49
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    @ChrisF OK, good to know. But on Drupal Answers I had to say about the same thing, like "use proper hook_form_alter" dozens times, sometimes copy-pasting parts of my older answers to save time. But the questions was not duplicates, they just happened to have the same solution (I'm in the top 10 rep there as far as I can tell, so I think you can assume I know what I'm talking). I tried to personalize them, but the core of it would be valid for many even without it. Should I really be blocked from answering in that situations? – Mołot Dec 6 '13 at 10:52
  • only one question - knowing how sloooooooow is SE team in implementing really useful feature requests, I wonder when I will be able to put a bounty on this one – gnat Dec 6 '13 at 10:53
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    @Mołot - that is the edge case. I don't know what the answer is there though. Though you say you are copying parts of older answers, so in that case you won't trigger the flag/message as your answers aren't exact duplicates. – ChrisF Dec 6 '13 at 10:57
  • My guess would be to encourage user who tries to post it, to make it more personalized answer - might be useful no matter if answer as written at first would be flagged or blocked, it might be an useful thing to do, wouldn't it? But as you know I didn't knew it's there so I didn't have time to think it thorough. Just wanted to make sure you know there is a case that does not exactly fit your post. – Mołot Dec 6 '13 at 11:00
  • What I often see is you mark a question as duplicate in the comments, another user adds an answer which is upvoted and marked as a solution and therefore gains even reputation for answering a duplicate question. While (please correct me if I'm wrong) marking it as duplicate in the comments does not give any reputation points. – Bas van Dijk Dec 9 '13 at 10:22
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    Wait, do really exact duplicates are so often? Even spam is usually randomized a bit... Anyway, making exact duplicate non-exact duplicate requires only single trivial change, yes? – Danubian Sailor Sep 1 '14 at 11:58
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    At the moment the system auto-flags as a duplicate answer if for example the user deletes the answer from one question then re-posts on a second. That can happen when for example they post the answer in the wrong place to start with (easy to do with several tabs open). So blocking here at least might not be the right approach. – Joseph Wright Sep 27 '14 at 15:22
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I wouldn't want to completely block duplicate answers. Duplicate answers most generally indicate a problem with the post, rather than the user.

While keeping the current behavior (duplicate answers to be flagged), I propose showing the user with a notice, something similar to

Wait!

Was this question asked before? We noticed that the answer you gave to this question is exactly the same as [this other answer you gave to a different question](link to his other answer). Are the two questions the same?

If they are, please consider flagging one of the questions as duplicate of the other! This helps us keep the site clean and your original answer easier to find!

If the questions aren't the same, please consider editing your answer to match this specific question.

The bet here is that the user's workflow is interrupted and so he'll at least absorb some of the message. If the user opts to submit his answer regardless, the same flag should still be raised.

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    I agree. Duplicate answers doesn't inherently mean that the question are dupes. – ɥʇǝS Mar 22 '14 at 19:51
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    @ɥʇǝS - but if they're not the answer should really be tailored to the specifics of that question rather than being a straight copy/paste of something else. – ChrisF May 11 '15 at 15:19
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I agree that we have a problem with duplicate answers and I really like Madara's suggestion to warn the user posting identical content, but I also think there potentially could be a way to leverage the community to help with this.

Speaking as a mod on Stack Overflow, the duplicate answers to multiple posts is a big problem that should be addressed. Just to give some perspective on how bad the problem is, we have 215+ duplicate answer flags in the moderator queue (based on 5/11 numbers). That means we have a single user posting identical answers to more than 1 question, in tags that we may or may not have experience it. Yes, moderators need to handle flags in all tags but each one of these takes a lot of time for us to process and when we don't necessarily need to be involved here. I think that these types of answers/flags could be handled by the community that knows the content.

My suggestion would be to create a new review queue for the duplicate answers. This queue would be filtered automatically based on your participation in the site, meaning if you've asked/answered in the tags then you'll be shown the items flagged.

The queue would show the content that generated the flag to determine the questions are duplicates. The reviewers would judge the validity of the duplicate posts (both questions and answers) and vote to close as dups and delete the duplicate answers.

The workflow details need to be fleshed out a bit more but this is just a suggestion that might help with handle the duplicate content problem that exists.

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    I've got a half-baked idea on how to leverage the 'Thor's Hammer' users more effectively for this, possibly through a special queue, but I think we can use the close queue for this just as well if we do it correctly. Putting a -review on the feature request, if I have not come back to this with a concrete idea by the end of the week, please let pings rain down on me. – Tim Post May 11 '15 at 15:27
  • @TimPost Challenge Accepted! starts writing bash curl script to ping Tim every hour a week from now – Madara Uchiha May 11 '15 at 16:11
  • @MadaraUchiha I'll make you famous. – Tim Post May 11 '15 at 17:43
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    @TimPost Is it good famous, or public execution famous? :) – Madara Uchiha May 11 '15 at 18:37

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