The front derailleur should shift the chain between chainrings without throwing the chain off the extreme outer and inner rings. It is possible that the front derailleur will rub the chain slightly even on properly adjusted bikes. This is likely on some bikes when riding in the largest sprocket in front and the smallest cog in back. As the bike is pedalled with force the frame flexes and moves the chainrings side to side, which cause an intermittent rubbing noise. Loosening the H-limit would move the front cage out more, and may stop the rubbing, but it may also cause the chain to shift over the largest ring and come off. Assuming you have the correct front derailleur so there are no compatibility issues and all aspects of front derailleur adjustments are correct on the bike, and you are not 100% happy with the performance you are simply exceeding the engineering and design capabilities of the mechanism.