Note: this concern is, as far as I know, only related to Xbox 360 owners.
As Xbox players, we know that nearly everyone who plays online does so in Party Chat. Party Chat blocks your voice from coming through in-game. One can therefore assume that if you are in a party:
- Your character's lips will not move, as the game is not picking up your voice.
- Yelling at a clerk will not function properly, due to the game not picking up the voice.
Do you think the folks at Rockstar have foreseen this problem and have planned a workaround?