In the past century, glass chalkboards and reverse writing were actually used in the military, mainly in air defense. Specially trained writers were putting objects scanned by radars on the board with coordinates and related info, while officers were reading them from the other side.
As a left handed person, it’s pretty easy for me to write backwards. It feels like something in my brain wants the letters and words to go that way, even though I never practice.
A right handed person can write in reverse with their left hand without much practice, by holding a pen in each hand, pretending to write with their right and mirroring the hand movements. It's even easier if you just "write" with your finger, eg on a foggy mirror, rather than holding a pen. The scripts we use are definitely optimized for right handed writing.
