When I click the hide chat button, the chat disappears as expected, but the chat surface expands with like 15 pixels to the left, covering a small amount of the stream while using theater mode. It’s nothing significant, but it’s annoying.
Specs:
16:9 / 1366*768 resolution
Firefox 40.0.3 (although this has been present for months on earlier ff versions, too)
Sadly, it’s not the browser. Tried it with the newest Opera and on Win8.1 64 bit with Internet Explorer. All of them produce the same problem when hiding the chat.