Wait, this should be marked Iimplemented], resetting it DOES restore it to undismissed. That's the actual function it doesn't reset anything else.
From the acp:
Please confirm that you want to reset the following notice:
Resetting this notice will display it to all of the users matching the notice criteria, even if they have previously dismissed it. Note that this will not restore the notice to guests who have dismissed it.
Tested. Body and settings, intact.