My question on SoftwareRecs Diff tool for XML files? has a comment 'possible duplicate' of the off-topic https://stackoverflow.com/questions/9713406/free-xml-compare-tool on StackOverflow.
I have seen this meta question What should I do with a question that has an exact duplicate closed as off-topic? where the approved answer says "Flag it as a duplicate" with the argument "Some day that other question might get re-opened".
In my case that is very unlikely to occur unless the rules for off topic change (asking for resources on SO). Even then I doubt that it will ever be reopened.
I have no idea what the policy/practice is about disappearing off-topic questions. If they disappear I would argue that my question should not be closed as duplicate (and I will add a comment saying so), and maybe even copy some answers, but that contradicts the above meta question.
What to do?