tl;dr buy a keyboard cover if you have this machine, or just contend with cleaning under the key with alcohol.
I've had a fairly good experience with the keyboard on these machines. The 12 inch MacBook had a perfect keyboard. I love the low travel keyboard and they really got it right.
But then on the MacBook Pro, it seems like the butterfly mechanism was changed to make it more susceptible to foreign matter causing key malfunctions. Admittedly I eat at the computer, so this is probably my fault, but the 12 inch MacBook didn't do this.
Either way, every time oddities like double characters or non-responsive keys happened, I'd carefully pry up the key, use a q-tip soaked in 70% isopropyl alcohol and just clean out the area. You have to get a LITTLE bit of alcohol into the actual switch dome. Basically, you take the q tip with alcohol on it and dab the middle of the little dome madly for a while. Then you stick the key back on and it usually works.
I got really unhappy about how often this started happening, especially since some keys' retention clips broke after so many removal cycles, so I just bought a silicone keyboard cover (the MoKo) one off Amazon. It held the keys in place.
No more problems. That's what it took. It works great now. And the cover doesn't even make it terrible to type on, due to the low travel.