So I was reading an article or something, and there was a sentence that quite intrigued me.
a. You can turn everybody against you, but never your boss.
"But never" is used as a coordinating conjunction, and it appears one adverbial phrase ("against you"). Even though I think it is idiomatic, I do not know for sure if it is grammatical. If I use "and" in this manner…
2a. You can turn John against you and your boss.
… the meaning changes. Now it coordinates the prepositional complements, "you and your boss". The only way we can work it out without ambiguity is this way:
b. You can turn John and your boss against you.
There are some other examples. An object complement ("do it") is in the position of adverbial prepositional phrase, still making the coordinating conjunction somewhat distant from the subject being coordinated as with an adverbial phrase above. Sentence d is an example where the object complement is shifted out of the way.
c. I made him do it, but not her. (sounds fine)
d. I made him, but not her, do it. (sounds fine)
Now with "and" in the same construction:
2c. I made him do it and her. (sounds wrong, and possible to be
misunderstood)2d. I made him and her do it. (sounds fine)
FINALLY, THE QUESTION: Looking at it, I can only conclude that "but not" is much more flexible than "and" when discussing idiomaticalness. However, is it grammatical to position "but not", a coordinating conjunction, so far away from its subject of coordination (what is being coordinated)?
And is my reasoning that the coordinating conjunction "but not" can be distant from its subject of coordination correct?
SECOND THOUGHT:
Is it because of the commas "but not" and" "but never" acquire that they are able to be distant from their subject of coordination?
When I put commas in sentence 2a and 2c:
3a. You can turn John against you, and your boss. (somewhat better?)
3c. I made him do it, and her. (still sounds wrong)
And when I don't put commas around sentence a, c, and d:
4a. You can turn everybody against you but never your boss. (sounds
fine)4c. I made him do it but not her. (sounds fine)
4d. I made him but not her do it. (? not so sure)
So to me there are some changes when I include and do not include commas. But I'm not a native speaker, and therefore I'm not entirely sure.
Best Answer
It is grammatical. Also, you seem to be confusing the issue with the coordinating conjunction. The coordinating conjunction is superfluous and can be eliminated entirely.
Example:
Your adding "but" isn't necessary, and this has nothing to do with coordinating conjunctions. It is completely grammatical to add a contrasting "not" phrase, or complement, to the end of a sentence. It's done with exceeding regularity.
Click the following link, and scroll down to rule seven: http://grammar.ccc.commnet.edu/grammar/commas.htm
As an aside, you'll notice that I didn't use the following example of yours in my above answer:
This is a poor example because it's unclear what it even means. It can mean that you can never turn your boss against you. It can also mean that you can never turn everybody against your boss. Owing to this lack of clarity, I chose not to use the example in my answer. Know, however, that the "but" you use in it is just as unnecessary as the "but" in the example of yours I did use.