Since I've never written a GreaseMonkey script before, I borrowed heavily from this script and basically played around with it until I got what I wanted. So credit to them for helping me get there.
I don't like having my chat window fill the full monitor, but I found that with my preferred browser window size I usually could only see 5 or 6 of the starred messages in chat. I was getting sick of it and decided to make this script that allows me to hide the room info (which I'll be happy to never see again) and the user list so that I can always see starred messages without having to resize my browser window.
The Room info is hidden by default (because how often do you read it, really?), and the user list is shown. For my preferred window width, that's enough to see all starred messages. There are toggles so that the room info and user list can be hidden/shown.
Get it from the Chrome Web Store