If you go to your favorites, follow the link through to unfavorite on the page, press the browsers back button to return the favorites page, the post is still visible because of the browsers cache, clicking to unfavorite here results the page counter-intuitively becoming a favorite again. Would it be possible to check if the favorite status on the client and server are in sync before toggling the favorite?
This is pretty minor, to my knowledge you're the first person to notice it since favorites were introduced. Furthermore I can think of at least 3 other places where similar disconnects with toggle-able states and history are possible, that I'm fairly certain no one's every reported.
Any "fix" would also be a bit cumbersome, either throwing a message up or not toggling... but only on the first click; and would be a special case for favorites.
Not worth changing basically.