I think I've been able to do this in the past, but I cannot see any way to do that right now. If it is possible, can someone point me in the right direction? And if it isn't possible, why not?
Yes, you can still do that. Go to the Niche details page (where you can see the list of actions, like when the auction ended, when the moderator elections started, etc.). Click the three dots in the top right corner. You'll see "appeal to Tribunal."
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