I assume something changed overnight at your end.
After marking all as read everything seems to stay as un-hilited (not green or red) for a while. e.g. I can refresh a forum index and see that there are updated topics but the buttons are still white.
Suspect that it is limited to topics that were just marked as read and would now show as updated (red).

Chowhound
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GameFAQs
GameSpot
Giant Bomb
TechRepublic