That’s owned my Microsoft, and they wanted to ban people from games using the Kinect by listening if they say “bad words”
That was a bug on the game developer’s side that passed player voice through Live as if it were an online match.
It was also 8? years ago; MS has changed radically since then, they’ve even become the single largest contributor to open source projects.
Regardless, Mixer is unlikely to overtake Twitch anytime soon barring a total collapse of Twitch and Google dropping the ball in directing people to Youtube Streaming. Mixer is very focused on integration with games and user interaction in chat (ala viewers can play minigames in chat, or even have chat affect what happens in games). AFAIK they have very little in the way of free-form podcast style streams that dominate Twitch.