I think the site would benefit from a hierarchical structure to the duplicate question functionality, indicating which questions generalise others.
I was contemplating duplicate questions last night in the context of some of the problems with this site. Thinking it through, many of the problems surrounding deletion of homework / psq's arise from limitations in the duplicate question functionality.
This is because maths is a relatively unique case among Stack Exchange in that as a general rule, maths questions and answers generalise other maths questions and answers.
Then long-time users and better mathematicians easily see that the site is, over time, deluged with a vast array of different questions which are simply new examples of the same thing. To the asker, the new question is not on the site, but a more experienced mathematician instantly recognises it as a new special case of something seen many times before.
If we had a hierarchical duplicate question functionality which indicated whether some duplicate generalised, or was generalised by, another question, it would be possible to navigate a hierarchy of generalisations. This would actually be a powerful learning tool enabling users to learn much more than simply the answer to their question.
A user could not only navigate to a generalisation of their question, but would also be able to navigate among other examples of the same thing.
For example: the OP says "How many distinct ways are there to arrange the letters in the word permutation?"... plus appropriate context etc., and makes it a great question (great for a mathematician of that level - obviously this will never be great for a professor of combinatorics). Then this is easily answered by somebody helpful, but also marked as a duplicate of similar great questions involving permutations of other 11-letter words with 2 duplicate letters. But all of these are identified as duplicates of the best generalising duplicate which covers permutations of $n$ elements with $k$ duplicates.
Then the question says:
this question is a duplicate of , and
this question is generalised by...
It would be easy and natural then, to give the generalisations of questions greater prominence in the site, and subsequent users can quickly use the fabulous duplicate question functionality to navigate to the question with the appropriate degree of generalisation for their needs.