Over at Worldbuilding we periodically receive new users who (not surprisingly) don't believe they need to take the tour or read the Help Center pages before they use the site. Call it being human... and we suspect other sites face the same problem. It's too common that the result is a 1-2 sentence question that doesn't have anywhere near enough details or is too broad (violates the book rule). And that's assuming it doesn't trip over most of the expectations in the Help Center.
We'd like to ask that new users (say up to rep 500) would be required to fill a minimum number of characters before posting a question. We believe this will contribute to their having to think through why they're being limited ("my question makes perfect sense! What's going on? Oh...").
I'd like to recommend a minimum of 150 characters.
(My thanks to user Surprise Dog for allowing me to ask the question. You can see an example question here.)