Why does not this thread change to read after visiting it?
 

I'm talking about this thread:
vBulletin 4.0.4 Maintenance Release - Now Available

I've visited it many times but when I go to vBulletin Announcements it's still shown as unread (in bold) to me and the "Go to first new post" icon http://www.vbulletin.com/forum/image...s/firstnew.png is there.

and when I'm on home page it shows the "Contains unread forum posts" status icon http://www.vbulletin.com/forum/image...rum_new-48.pngfor the vBulletin Announcements

I made it as read only by double clicking on the vBulletin Announcements forum's status icon.

Is it just me how is seeing this?
Is it a bug or a feature?