The addon has a lot of promise, but compatibility with Firefox 57+ WE still needs work. It's often buggy. Things like Shift-F open in new tab doesn't work. I hope as developers get things worked out with Mozilla and the new APIs many of these bugs will be resolved.

The main issue right now is the inability (as far as I can tell) to customize keybindings.

Very promising extension!

With one question:
why is it disabled on addons.mozilla.org?

New: Not working on news.google.com!

Update: Sorry I did not describe this properly. It is actually shift-f that does not work, and it seems it is a problem of Firefox WE API. Thanks for your great extension!