Most actors I've come into contact with, if they're not ok with it, they will tell the director/stage manager so. Some actors are very much ok with notes during the half-hour. If someone is not ok with it, but doesn't tell anyone, except the actors, this is where the deputy comes in, they can talk to the director/stage manager themselves (in person or via email) and if that does not work, they can go to equity, and mention the breach of contract. As for the director giving them notes after opening, as a stage manager, I would suggest the director give the notes to me, and so I can give them to the actors, and if it comes to a point where actors don't come in before the half, nor do they want notes after the half. I will catch them before they leave, and if not, I will write out notes, and leave them someone at their station in the dressing room.