If you spot a duplicate Niche you should appeal it to the tribunal.  There are several ways to perform this activity:

• For an existing Niche that is "Active" (owned), go to the Niche page, click on Profile, and then click Appeal to Tribunal.

• For a Niche is the “Approval” stage simply downvote it and select the reason as “The Niche is redundant and duplicates an existing Niche.”

• For a Niche that is in the “Auction," click on the Niche name and then Profile, and click the Appeal link.