Keybinding issues: unbinding chat from slash and enter, and binding Z at all

The enter and slash keys are permanently bound to chat; enter cannot be bound at all, while slash appears to allow itself to be bound to another command in the menu but will still only open the chat when it's used. I'm left-handed, so these keys are useful and having chat mapped right next to my movement keys means I accidentally open chat more often than I'm comfortable with. Is there any way to rebind these keys or otherwise unbind them from chat?

Also, when using a Dvorak keyboard layout, the Z key cannot be bound to anything. I presume it's because on a QWERTY layout that key corresponds to slash? Is there any way to bind the Z key without having to change my keyboard layout?