Maarten De Queecker
Agreed, but we are in the 21st century now, and nobody uses swords anymore, except for practice, so why is it still wrong to practice left-handed? My swings with my left hand are technically of a higher level, feel more natural, and are stronger. I also feel more relaxed, since I have to think less and I can move more fluidly. It makes no sense at all to train hand-to-hand combat on both sides, but do sword techniques that represent the hand-to-hand techniques only with one's right side.
There's absolutely no reason not to do suburi (or practice cutting on a target) left-handed. Even if you are right-handed. And, if you are left-handed, doing suburi right-handed is also good. You learn to cut with the whole body, and not cheat with your hands.
The vast majority of kata, however, are designed for two right-handed swordsmen, so it behooves the left-handed person to become proficient with right-handed cuts.
I'm lucky(?) in that the sword art I study includes a few left-handed forms. But they're rather tricksy.