When a question is migrated to a different site, the copy on the original site (the migration stub) has "[migrated]" appended to the title. Here's an example. On the question page itself: In the user's question list: But in search results, "[closed]" is appended instead: What gets appended to ...

This will be fixed in the next deploy. That page just wasn't querying for the "duplicate"-y-ness of questions.