Look at this question. The title and question body are the same. I think this is not a good practice. Is it possible to create a mechanism to force a user to give a brief description which is different from the title?
As unlikely as it sounds, people do occasionally ask on-topic questions that are in both the title and body of the question.
This doesn't happen often enough to warrant a system change to detect it, and users will just get around it by adding extra junk characters to either the title or the body, which makes the cure worse than the cold.