I was under the impression that if Question A is closed as a duplicate of Question B then they are linked, meaning that if you view Question A then you will see Question B in the sidebar among linked questions and vice versa. (This relation is symmetric.) I think that seeing duplicate questions in that list might be sometimes useful, see my answer here. (In fact, one of the reasons I am asking this is the recent discussion about duplicate posts.)
Indeed when I look at an example of a recently closed duplicates like Intuitive explanation of concentration of the measure for spheres and it behaves this way: How to explain the concentration-of-measure phenomenon intuitively?
But I have noticed an older pair of duplicates: Cardinality of symmetric group and and Cardinality of the permutations of an infinite set (It was closed in 2010, i.e., pre-migration.) The duplicates are currently not shown among linked questions. (See screenshots below. The linked question can be also seen here and here, but this links display the same questions - which, I guess it not surprising. The latter question has one linked question, but it is other question, not the duplicate.)
- What are the reasons for this behavior?
- Is this connected to the fact that the closure was before MathOverflow joined Stack Exchange network? Do all pre-migration posts behave in this way? Or is there some other reason? (Additionally, is this MO-specific, or does the same problem occur network-wide?)
- Other than simply adding a link somewhere (by adding a comment or editing one of the questions or one of the answers) are there some other ways to correct this? Is it possible to make the correction for all questions rather than update links manually one-by-one when you encounter situation like this?
EDIT: Now I have noticed that this comment (on one of the questions mentioned above, posted pre-migration) has links to two other questions (infinite permutations and Definition of infinite permutations) which are not shown among linked question either. (The only question which is shown among linked questions appeared there because of a comment I posted today.
So it seems that this problem is not only with duplicates, but also with other links.
This question probably might be asked on meta.SE, but since I thought that this behavior might be related migration of MO to SE network, I have asked it here. Maybe I am wrong and this is not MathOverflow specific and the same behavior can be observed on other sites. (If that's the case, then meta.SE would definitely be a more suitable place to ask this than meta.MO.)
I also was not sure about the bug tag, but I will leave the decision whether it belongs here to more experienced users (or mods and SE staff).