[nickonline]

With Starcraft 2 there's a feature to "watch a reply with a friend". Perhaps this is an easy way for them to get the same functionality without having to build in a replay viewer

There's also a whole audience of people on twitch who watch live streams of games with merely the player commenting into their headset as they go regarding why they're doing something (sometimes not even that!).

So there's two instances without editing already in wide use today.