Images were deleted from imageshack.
Basicall, you loose image of arrow (shown in the first post of the read and you can see it here on vBorg) before thread title that lead to first unread post (or last post of the thread, depending on thread read status). You have only thread title as a link and it has function that arrow image does.
If you ever was on any Xenforo site, you know how links work there. This makes vBulletin site works in that way also. Which is more logical in my opinion, I hate when I need to target small image when I have large thread title.