Hmm I think it's the stylesheets that cause it not to display new topics and replies since last visit.
I switched to use "Serene Silver" and "Default", and I could see new topics and replies, it also changes the "thread title" cell row colour to silver for unread, and blue for read. Although visiting a section with new posts and replies and refreshing or backing out without reading the posts will cause the indicators to disappear.

I cant see if it works with 'main index' since it still thinks I'm not logged in if I go there.. same thing in IE (shudder) too..