A nice example of the Challenge Day System at work was when Queen Shuri was challenged by a member of the Jabari Clan.
The challenger's grevivance was that Shuri was not fit to rule because of her wild party girl reputation.
The challenger was able to express his thoughts unabashly and Shuri was able give her position on the matter. She won the contest and dealt with an area of dissent at the same time.
The story appeared in a Marvel Legacy one shot written by Mayberry if I am not mistaken.