Edit: I just found this query that does what you want:
Posts that are the targets of the most duplicate closures. On Meta, currently, it seems What can I do when getting "We are no longer accepting questions/answers from this account"? is winning!
I seem to remember there being a page of "questions linked to this"
for each question, but I can't find that page now...
If you want to find all the questions linked to a specific question (not necessarily dupes), the URL would be:
http://[site]/questions/linked/QUESTION_ID
So for this question, it would be:
https://meta.stackexchange.com/questions/linked/256607