This is something I don't quite understand. I have a hypothesis (based on observational anecdata) that left handed people generally don't use a dynamic tripod pencil grip, often times there is a fair bit of flexion at the wrist which result in the palm going over the wet ink. Otherwise how are RTL scripts (like Arabic and Persian) not encountering similar issues on right handed people? In fact those scripts require joining, and their calligraphy can get incredibly floral.

Ah, but you get your revenge when it's time to write in an RTL script.

Use boustrophedon for equality!