All right, to spell it out: Merriam-Webster is not a dictionary of "correct" forms. The usage of "literally" in my post is documented in Merriam-Webster as "used in an exaggerated way to emphasize a statement or description that is not literally true or possible." It would be inappropriate to use "literally" in that way in a science article in the New York Times, because the standards for writing in the New York Times are different from the standards for inclusion in the Merriam-Webster dictionary.