In the current version of mojoPortal the title on Thread.aspx is pagename - thread subject, where pagename is the name of the page containing the forums. On this site the page name is Forums so it is Forums - Thread Subject.
Given the character limitations of title, it does not seem wise to add the forum name.
I can see where someone might want to leave out the page name and use only the thread subject, so I've implemented a config setting that can be used to make that happen. In the next release of mojoPortal you could add this:
<add key="Forum:UsePageNameInThreadTitle" value="false" /> (the default is true)