Windows 7, Chrome.
So this is a two parter;
The resizing with the chat popout is broken on livestreams. If you resize the window with the popout open, the video display will shrink, in what looks like completely broken formatting.
The second part, is when you have the popout and somehow managed to get the resize right first try (there is no scroll bar when chat popout is open and the video has sized to the window) the chat overlay will appear over the video player. I'm not sure of the cause but it may be when a new poll is created.