You have to do this using a real, full size keyboard, that has a separate numeric keypad area, such as a Tactile Pro. 1. Open a Terminal window. 2. Type "nano" and press enter. 3. Press any number on the separate numeric keypad area, such as "0" (zero). 4. You will not have the expected behavior. (I cannot easily compare 10.12 to 10.11/10.10, only to 10.9, so I don't know if 10.12 is actually the first version with this problem) This is on a MacPro5,1 with a brand new macOS "mack-oss" Sierra / Mac OS X 10.12.0 installation.