Here's why:
* One question mark is enough. A single question mark signals the end of a sentence and indicates that it's a question.
* Double question marks can be confusing. They might make the reader think there's an error in the sentence or that you're trying to emphasize the question, but it doesn't have a specific grammatical function.
If you want to emphasize a question, consider using other methods:
* Capitalization: "ARE YOU SURE ABOUT THAT?"
* Exclamation mark: "Is this really happening?!"
* Bolding: "Is this a joke?"
* Context: Using the question in a context that makes its importance clear.
Remember, clear and concise communication is important. Stick to standard grammar for the best results.