Was thinking that local chat is a bit to large. When u come to a tribe and starts talkin to them, perhaps dealing with one or several traders at a trading post, the entire zone hears u and your talks are mixed with others talking also in local.
Therefor I suggest that local chat should be just that, chat within earshot and not entire zone. Instead, introduce a zone chat for that. And then we have yell for the entire world (for them with awsome strong lungs).