Specific to wikimedia Talk pages?
On https://www.mediawiki.org/wiki/Talk:Flow_QA - when there are new unread messages present, an additional messages is displayed: "You have new messages"
When 'Mark as read' is clicked and the counter goes to 0, the message does not disappear - even after refreshing the page.
Another sample was on http://test.wikimedia.beta.wmflabs.org/wiki/Talk:ET37. "You have new messages" did not go away after
- refreshing the page
- navigating to a different page