At my local race rides, it's often a full on race. Go where you need to go but keep it safe. I split wheels all the time. Sometimes for better draft in crosswind, sometimes getting ready to move when I need to, sometimes to purposely keep other riders off either wheel, so I can take my pick when I need to. And sometimes I'm the one pinched to the right. If his bars are in front of mine, tough luck, I have to ease up or get aggressive. If it's not a real race, it's usually just ease back and let him have the space.