BuddyPress.org

I think that your homepage display, whatever that is, is the abnormal one Adam. The admin bar is supposed to fit across the entire width of the display. That’s the normal behavior. You can modify this by creating a file in your home theme folder called site-wide.css

That needs to live in a directory called /themes/<your theme directory>/css

Within that file you can put any css you’d like to control the appearance of all bp components.