I am fine with the ticker (the small button down right). But when I am in Facebook, I have to tick it every time and then the chat sidebar hides.
If you want to hide the chat automatically, then this most likely means you don't want to chat at the moment.
Select "Unavailable to chat", then hide the sidebar.
Any future requests to the Facebook homepage (whether you are logged out or not) will have the chat window closed.
I see today that if you hide the sidebar it sticks like that at the next FB visit.
So either Facebook changed back to how it was before or I didn't know that happens.