There's a post over on MetaStackOverflow which explains some changes going on across all StackExchange sites: Changes to "close as duplicate" (part deux). I recommend reading that for the detail of what's going on and the thinking behind it but highlights from that post include:
First, some background: we're taking a look at closing behavior and trying to figure out how to make it less jarring for new users. Our goals are (1) to make it clear to people why their question got closed and (2) to make it obvious what they can do to fix it or get better (3) in order to reduce the likelihood of getting into an argument about whether this should have been closed.
We started with dupes.
What do we want to tell the user [...]? Something like, “Somebody already asked this. If that other question doesn't solve your problem, please clarify your question to explain how it's different.” Perfect: if the other question helps them, they're happy because they got an answer. If the other question doesn't help them, they know exactly what to do.
So here are the changes we made:
We've changed the instructions everywhere to indicate that the answers to the original question must solve the dupe’s problem. That means that the original must have an answer.
When a question gets closed as dupe, instead of just saying "Possible duplicate", we now indicate "This question already has an answer here".
If the owner comes back and edits their closed question, it will automatically go into a reopen queue. There's even special UI to compare before and after and see what changed.
The "Close-as-dupe" popup now makes it much easier to find dupes with answers by allowing you to search and preview questions and answers within the popup.
We now show "[duplicate]" in the question title everywhere, instead of "[closed]".