Bike Friday for knock down packing,
uses a slitted sleeve, around the bars, that is held in the stem
with 1 small bolt in the center of the face plate
inside the handle bar section, there is an inner sleeve.
so it's plenty strong.

loosening the 2 face plate bolts allow the bar to slide out of the slotted sleeve

On my touring bike, I had 2 narrow bars, cut each to become 1 wider bar.
and Joined them in a 4" wide open face stem..
not a quick release scheme either , but iT made packing for travel
as checked luggage easier..

recently I got a Bike Friday , the bike has their optional folding handlebar riser,
then the bar folds down ..QR, Lever + a spring loaded button lock and a pull up
lets it fold over..