>The point here is that if I'm in the messages area (therefore already logged in), and then click the homepage, or just navigate to UT from a new tab/window, there's still the login dialog, although I'm already logged in. If I forget that I am, and log in again, I get a new messages window which contains only new messages since the last refresh in the first window.

This is because the browser is configured to not broadcast the session to other tabs. This is not the default. There is a setting for that in the browser. I just do not remember what it is but it is not the default behavior. The default behavior is to recognize the session across tabs.