I've noticed that a lot of bad questions aren't even questions (have no actual question in them). They usually go something like:
I'm trying to do X. It should do A, B and C.
I realize that these "questions" can easily be be translated into
How do I do X? It should do A, B and C.
Is this something we should try to prevent? If so, what can we do?
The most simple thing would be to inform the poster of a question that their question doesn't include a question mark. I may cause them to rethink their question before even posting it. The presence of a questions mark could either be enforced (i.e. you can't post a question without it) or just encouraged (i.e. the questioner get informed about the missing question mark but can still post the question).
I could also see the possibility of a more advanced heuristic that tries to inform users that it looks like they are posting a question that probably is not a good fit for the community.
?
is rather meaningless. Bad questions will be bad with or without enforcing this.