It's a letter in which a student presents arguments against smoking in public places. I wonder if 'that' should be used in the sentence after I could not agree more that ... and if it is appropriate style for such a letter to the editor.
"That" is OK, and the style isn't a problem: I just think it's rather an odd thing to write. You use "I couldn't agree more" when you're wholeheartedly agreeing with something that someone else has just said. How does that tie in with writing a 'letter to the editor'?