Here is my first attempt at stating a pattern..

Pattern Name: FeedbackThroughChallenge

Some game systems allow open ended responses without providing feedback
therefore allow users to challenge each other on the correctness of a given response.

Principle involved:
Learners must be provided with timely feedback regarding their performance and learning.

Sample Situations: Scrabble, Boggle
In Scrabble users create words from letter tiles, Users may create words that violate scrabbles given words or are mispelled. Opponents have the option to challenge the player.