Existence of multi in US English Yes, the prefix multi is valid in American English, and usually used unhyphenated You can see dozens of examples on Wiktionary or Merriam-Webster If your grammar and spelling checker fails to accept it, it should be overridden manually
Why does the multi-paragraph quotation rule exist? The answer to this question clearly explains the standard rule that when you have multiple quoted paragraphs, each new paragraph starts with an opening quotation mark, but only the final quoted par