Key remapping without Karabiner
Sadly, with MacOS Sierra, Karabiner has gone into a strange kind of hiatus-but-not-really-because-someday-we'll-fix-it.

Which is too bad, because Karabiner was the perfect tool for what I needed (which was make MacOS behave like a forty-year-old UNIX terminal because my stupid fingers still hit ^W to delete a word and I kill the window and I can't stop, no, don't help me, I'll die eventually and then my problem is fixed). 

My other main tool is Typinator for abbreviations--w for with, h for the, n for and, etc; those really add up.

So far, I've found BetterTouchTool to be a viable replacement for Karabiner, even better in some ways. But worse in others; key repetition doesn't work for me despite the developer saying it does. (Possibly it interacts with Typinator, but turning the latter off doesn’t fix the problem.)

I've written a whole novel using these two tools (Typinator and BetterTouchTool), but I'd appreciate anyone chiming in if they've found something better still.