Circular duplicates strike again

Question

It looks like this issue has come up before, and been resolved, but it just happened again on Travel.SE. Perhaps this is another corner case? These two questions are closed as duplicates of each other.

• https://travel.stackexchange.com/q/52423/444

  

• https://travel.stackexchange.com/q/52424/444

  

I had the last vote on each, although in both cases, my vote was for "Unclear what you're asking", but the weight of votes in both cases were for the duplicate status. So if the existing checks are only in place at the time someone casts a close vote, that would explain how this one got in under the radar. Perhaps another check needs to be done when the question is actually closed, not just when close votes are cast?

And as @gnat points out, low-rep/logged-out users get a Redirect loop when trying to load either question.

^{NOTE: A moderator has already fixed this particular circular duplicate situation by closing one of the questions with a different close reason.}

Answer 1

Rather than checking at the time of closure, it seems like a better idea would be when a question is closed as a duplicate, look at the duplicate question(s) and clear / instantly age away any duplicate votes that point back to it.

• The votes are now invalid in a way. That question is no longer a valid duplicate target and the votes don't make sense anymore. We already do this for the similar situation of migration flags on questions which cross the maximum age threshold after the flag has been cast.

• It doesn't make much sense to let the fifth close vote override all of the other four close votes. That's one user saying something is unclear, where four other users just said it was a duplicate. Duplication doesn't inherently imply that the question should be closed for another reason, so that's essentially saying one user found it unclear and closed it unilaterally.

• Aging away the duplicate votes allows the users to eventually go back and re-cast close votes for other reasons if the question does need to be closed for some other reason other than being duplicated, in accordance with recent changes.

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This has now been implemented. It won't affect past circular closures, but will prevent new ones from appearing.