I have never thought about this,a nd not sure that it matters, but as a righty, holding knife in my hand, I like to be able to turn it so blade faces across body(ricasso at right side of body, tip at left side), edge down(ie a normal knife grip) and be able to see the makers mark
So I guess for a left handed knife, if you're looking down blade, with ricasso closest to you, tip farthest away, the mark should be on right hand side, the opposite of what I like as a righty.
Interseting question