Keyboard accents feature missing from High Sierra

Any antivirus stuff on your machine?

check your settings for key repeat rate and delay

try adding a french or spanish keyboard to system prefs/keyboard/input sources and restart

try setting up a new user account and see if it works there

The defaults command as you typed in your post is missing a space. Could have just been a typo in the post but if you typed exactly as it appears here it doesn’t work correctly without a space before -bool

I have had the same problem.

I upgraded to High Sierra from El Capitain. It did work before, it didn't then.

I booted in Safe Mode, I set something in the keyboard preferences (I changed the delay time), I rebooted, it started working again as it had to.

What program are you typing in? Works fine for me.