The no-mask thing is to allow full-face camera shots. Masks don't impinge on communications in any way, in fact they reduce the ambient noise into the mike. I think the Blue Angels 'no mask' thing is one of these classic bits of commander's risk analysis:
Option 1 - Keep the boom mic. During my 2- or 3-year period of responsibility, there is a small (perhaps less than 1%) chance that a serious incident will result in me being charged with negligence, for perpetuating an obviously risky
PR benefit at the expense of safety.
Option 2 - Mandate the mask. Approximately a 100% chance of attracting disapproval from old + bold admirals (who aren't themselves in the airworthiness chain, but definitely have a say in my career). I don't really want to be known as a stickler for health and safety, do I?
Less than 1% chance of being caught out? 100% chance of attracting criticism from above? No-brainer. Risk tolerated!