It's worth noting that this answer changes a bit if you're on the dining plan, just in case anyone is curious. For the most part, the answer is the same (no one cares if you share and some places will encourage it), but some non-Disney owned restaurants simply won't allow it. One credit per person, everyone eats. Via Napoli is the only one I can think of off hand, but it's notorious for not allowing say, one person to order with their dining credit and the other person to just share the pizza or so on. If you're off the dining plan, they don't care, and if you both order but share off each other's plates, they don't care, but they've been known to insist everyone uses a dining credit.
(I wonder what would happen if you only had one dining credit left when you dined there, but I don't often use the dining plan, so I can't really test it.)