Ground an Neutral to Neutral bar?
In a panel which is the service equipment (first disconnect), the neutral and ground must be bonded together. Since they are bonded at that location, there is no need to have a separate isolated neutral bar. Standard practice is to mix branch circuit grounds and neutrals on the same bar. Most panels are listed for up to 2 grounding conductors in each terminal hole, but each neutral must be in a hole by itself.
I am a lawyer, but not your lawyer. And who cares anyways? We're here to talk construction. This is DIY advice, not legal advice.