When you first create a new class, you get "no messages" in the method
category pane. Option-clicking it pops up the normal menu, including the
menu item "Rename...". You can select this item, type a name, and accept
it - but no! The name doesn't change. 

My RFE: disable the "Rename..." menu item when you click on "no messages"
- it's not available, so don't fool the poor newbie.