Your browser does not seem to support JavaScript. As a result, your viewing experience will be diminished, and you have been placed in read-only mode.
Please download a browser that supports JavaScript, or enable it if it's disabled (i.e. NoScript).
I've only seen it happen when in spectate mode (but I've seen it happening multiple times) Youtube Video
Another video of the same issue: Youtube Video
This is a really cool feature, and should be implemented on release