When you receive the message "Messages have been posted since you loaded this page" for ignored content and click to view the messages then no content appears at all. I guess this is as designed.
However, if there is also no other ignored content on the page, then the 'Show Ignored Content' link does not appear, and probably should.
Additionally, if there is already ignored content but it is for a different user, then the hover text is incorrect.
It would be great if any elements with the "ignored" class being added to the page would trigger the 'Show Ignored Content' to refresh itself (i.e., work out if it is required, update the hover text, etc.).
This would also help with the extension I'm developing which includes the ability to show ignored content on the Recent Activity page, as the same issue is occurring when someone tries to view older recent activity.