UPDATE: It looks that the requested feature is already in place...the body of the post that triggered this request originaly wasn't the same as the title, this was caused by an edit (I included the details at the bottom)
As I understand, only title questions aren't allowed on SE because we want questions descriptions longer than what can be included in the title and that a good title summarizes the content of the question body, not to repeat it textually, and there is no value added on having the same content both on the title and the body (I'm not talking about including the title in the body but about including the title in the body and nothing else).
I think that this might be implemented as an opt-in feature that the CM should be able to turn on/off on existing sites and on new sites during the alpha/beta stage this setting might be discussed on their respective Meta.
The current Ask page has three stages:
- Welcome modal shown only to new askers
- Drafting a question
- Reviewing with / without errors
The "block" might be implemented by highlingithing in red the body box and showing a text like the following:
Body should be used to provide details and any research
Image taken from "The new ask page is now live ..." announcement
Orinaly the question body wasn't the same as the title, that was result from a edit. I didn't reviewed yet the older cases.