Twitch seems to be on a roll with features and announcements lately, though some consider that roll to be a slice of moldy bread.
The latest 'feature' to be announced by Twitch is Audio Recognition, basically similar to YouTube's Content ID system muting videos with copyrighted audio.
The blog entry makes it clear that Audio Recognition is only in VODs, and not in live broadcasts. It doesn't clearly specify this in highlights, but a bit of further reading seems to imply that they are affected as well. Fortunately, only parts of the video will be muted (the parts with the copyrighted audio content and surrounding 30 minute blocks scanned by the technology used).
Already, the technology has already muted various video content in error (at least according to various sources). While the blog entry specifies that content owners should notify them of unauthorized content, it does not give mention of how someone can appeal falsely identified content, and instead suggests using Creative Commons audio or similar resources.
This 'feature' is part of a new partnership Twitch has with Audible Magic.