How do I turn off "Show Bluetooth in menu bar"? On macOS Sierra, if I go to System Preferences > Bluetooth, and uncheck "Show Bluetooth in menu bar", the symbol remains stubbornly visible.

How can I make it invisible?
Try holding down the Command key and using the mouse to drag the Bluetooth symbol off the menu bar. Alternately there is a check mark to uncheck in the bluetooth preferences in System Preferences.