In keybindings, there're different section and these section can have repeated keybinding, for example, z key in the keyboard can be used to prone or to control camera related controls under Spectating settings.
The problem is if you remove some key on spectating section and you try to reinserted that same key, the game is going to complain that you are creating a double assignment to that key and will remove that key for other functions! There's no problem in using same key to work differently in different circumstances.
