Ehmmm, the support for Sierra is on progress.

macOS Sierra support status

Karabiner does not work on macOS Sierra at the moment.

We are developing Karabiner-Elements which provides simple key modification for macOS Sierra at first. (Karabiner-Elements works well on macOS Sierra. We are working on fixing several remaining issues.)

We'll start updating for the full featured Karabiner for Sierra after Karabiner-Elements is completed.

https://github.com/tekezo/Karabiner-Elements