Last modified: 2013-12-26 14:50:58 UTC
The contents of the sitenotice fallback to Anonnotice for non users if it's message is not empty. However it's not dismissable.
DismissableSitenotice only checks whether the session is for a logged-in user or not. It calls into core code to get whatever the currently-applicable site notice text will be; presence or absence of an anonnotice setting will have no effect on this behavior. Fix would be to remove that one 'if' line, so the dismissible notice display gets used for all visitors. Should also double-check that the cookie for saving the dismissal state is properly ignored for caching.
*** This bug has been marked as a duplicate of bug 57732 ***