Uh oh, this will add to the conversation some. I never could figure out why a scissor won't cut left handed.
If you apply exactly equal vertical force on the top and bottom blades of the scissors it would not matter whether the scissors are left or right handed. However, when gripping a pair of scissors to cut something the human hand exerts both vertical and horizontal forces on the blades. Left and right handed grips exert these horizontal forces - which tend to force the blades together or apart - in opposite directions relative to the pivot point.
For maximum cutting efficiency scissors are designed so that your natural grip will force the blades together to improve cutting. For right-handed scissors you will have your right thumb
through the hole on the top blade and your fingers
through the hole on the bottom blade. When you cut, your natural right-handed grip will squeeze the blades together and you will be able to see the shearing edge of the cutting line on the material as you cut it.
LeftHandedWorld.com