Don't allow it in the usual way. I personally do not like listening to people drink, eat, shout, play music, swear, get told off by their mum, shout, be generally annoying, or insult me. If proximity chat is brought in can you allow us to configure it so we can mute everyone that isn't in our friendlist or fireteam. Then add an option so that if I do have it muted I can hold down a button to unmute so I can listen and an icon appears above my head to show I can now hear them. If the person is the annoying we can block them as usual. Won't be a good time having to go through the motions of muting people who fail to be civil every time. I think Bungie got it right to begin with, and if they introduce proximity chat its going to lead to the usual obnoxious and rude behaviour we see from a small minority of players.