Here’s an example: “Everybody but Jason stopped eating.” It wouldn’t make sense to put a comma after the word everybody because then you have a sentence fragment that isn’t telling us anything. And it would disrupt the meaning of the sentence.
But in the sentence, “I like ice cream, but not banana flavored,” the comma is well-placed. That’s because you have a whole clause that is not broken and it contains a pronoun, a verb, and the direct object.
What about “He chose not one but two tuxedos”? You tell me.
Sigrid Macdonald is the author of three books, including Be Your Own Editor http://tinyurl.com/7wnk5se and two erotic short stories, which she wrote under the pen name Tiffanie Good. Silver Publishing has released “The Pink Triangle,” a tale of friendship, lust, and betrayal. You can view her story here: http://tinyurl.com/6v65rgr