Bezatron

I've never played in a competition where someone can mark their own card! Simply swapping cards like you're supposed to solves the problem. If everyone has to do it then no-one is singled out.

If it was outside the course boundary it's OB. If it's not marked it's not a hazard so no lateral either way.

I'm left-handed and I've always played golf right-handed as it feels more natural. I bat right-handed at cricket too, so it's not to do with the relative scarcity of left-handed clubs.