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When a user see a list of Linked/Related Questions on right panel, it will be useful to have the word [duplicate] visible immediately after title. It will help to understand why the questions linked and should I look at them.
Note that if the question has too many links, there is a link at the bottom "see more linked questions" and it opens full size page, where [duplicate] status is shown after the title of each duplicate question. So the change will make linked questions presentation consistent.
Somehow related suggestions to make easier see duplicates:
Show questions closed as being duplicates on the initial question.
Show list of duplicates of the question