Been using master links for many years without any issues. The strength of a master link is the same as any other link so there's no reason for it to decouple based on the force exerted on it. Also the force is a pull, whether pedaling forward or backward and in order to remove the master link it needs to be pushed off from the side.

Not sure there's true merit to this but I've been warned about removing the chain via master link repeatedly though, as constant flexing of the clip could weaken it and cause potential problems. Never really had that issue though because I rarely remove a chain unless it's time for a new one.