This is cool UX and I want to know who verifies questions marked as duplicate.
What is meta?
- Any Stack Exchange user can ask a question
- The community provides support, votes on ideas, and reports bugs
- Your voice helps shape the way Stack Exchange operates
Ultimately everybody who uses the site.
Those with a reputation score of 3000 or more can vote to close, but anyone with at least 50 points can add a comment with a link to a duplicate and absolutely anyone can flag a post for moderator attention.
Then, when a question is closed other users can vote to reopen if they disagree with the original decision.