If you're left-handed, handwriting proceeds best by mirroring what the right hand would do (ie. write 'backwards'). It's far more natural. Alright, so others will need a mirror to read it - but that ought to be society's problem, not yours! ("Equal rights for the Sinisterous!")

In a gradual shift toward ambidexterity, I've found that questioning society's insistence on 'right-ness' can be enlightening...

Presumably script that proceeds right to left (and even upwards) was originated by left handed scribes

edit spellchecker : left handed scribes became left handed scones. The history of heavy baked goods in the development of human civilisation has been scandalously neglected by a blinkered academic community.

I remember I read somewhere about the fact that right-to-left script was preferred when carving script on stone. as right hand people supposedly prefer to hold the hammer on their right hand.

I'm not sure if that's really the cause. Furthermore in many ancient scripts the direction was quite unimportant, in some cases even reverting in each line (Boustrophedon).

Interesting take on direction of writing: http://shkrobius.livejournal.com/292987.html

I don't get it. Why is it harder for lefties? Aren't the pens themselves ambidextrous?

Writing left-handed in a left-to-right script requires the hand to move over the ink that was just applied. This invariably means smudges. Writing right-handed (LTR) the ink has time to dry before the hand moves over it for the next line of prose.

Plus the ink from a fountain pen stays "sumdgier" longer than modern pens.