As a guest opening a complete thread then clicking 'back to forum index' the thread title text is still bright blue and the icon and reply icons are red still.

Is the one link you clicked marked as visited?

No, as a guest if I click on a new post (bright blue text, red icon) read the post then click 'Back to the forum index' the post title still shows as bright blue with red icon.

As a guest, just say I have a new original post and 4 replies, if I open the complete thread and then go back to the index the original and 4 replies are bright blue with red icon.

as a guest If I open just one reply and go back to the index the original post and 4 replies are still bright blue with red icon.

As a user if I open the complete thread and go back to the index the original post and 4 replies are dark blue text and no red icon

As a user if I open just one reply and go back to the index that one reply text is dark blue with no red icon and the other 3 replies and original post are still bright blue with a red icon

I really want the guest read posts to work like it does for registered users?