I have seen several questions containing code that is poorly formatted and totally devoid of comments. One recent example is this C example.
For a short code block that might be acceptable, but it is hard to provide meaningful commentary on a long block of code where it may take a lot of effort just to figure out what it is supposed to do.
I'm confident that the submitters of those questions would get more answers if the code was a little easier to understand. Neither the How to Ask sidebar nor the faq mention this. Could they be updated?
I'm not sure there should be a firm rule that poorly formatted or commented code should get a question deleted, but it might be helpful to point out that reasonable formatting and commenting are more likely to get answered.