Never on 25 June 2014
Parental controls. Leave voice chat off by default so people don't assume you can hear them. Have it so you can easily report bad behaviour in game.
This is Nintendo. If they could afford to properly moderate it, and Nintendo gamers develop the right culture to readily report abuse. And make it an offence to spam annoying non-game related stuff in chat. They could actually be the company that shows how voice chat should be done.
