The font spacing settings appeared for me as well on both my Colorsoft and my Scribe; it seems Amazon has decided to enable the settings at large. For the record, my Kindles are jailbroken and have OTA updates blocked, so evidently the process by which settings are remotely enabled on a device does not rely on the standard OTA binaries.
@JSWolf, I’m lazy to take screenshots now and my Kindles’ menus are in French anyway, but you can see the settings in
this Reddit post.