In addition to having that little flag icon which identifies a member's home country, I'd be interested in something that identifies other players' primary languages. If I knew an opponent's primary language wasn't English, for instance, I could avoid using slang when messaging him or her.
I realize that members can always put that kind of info in their profiles, but making it a selectable option would, I think, encourage people to use it.
Ideally, such a feature would display "Other Languages Spoken" as well as "Primary Language." I'm curious to know what others think of this idea.