I got my first sleeping bag when I was a Boy Scout in the mid-1960's. Since then I've owned quite a number of bags, mostly mummies, all of which sported a right-hand zipper.
I recently bought a heavily-discounted Marmot Helium Long at REI and immediately noticed that it came with a left-hand zip, which I thought was a bit unusual. The salesguy said that most men's bags have left-hand zips now, and women's bags have the righty zips. I had never heard of this, as all of my previous bags from such companys as TNF and Western Mountaineering and Sierra Designs all came with right zips, but admittedly these are all a few years older.
I must say that I have taken to the left-hand zip easily and now actually prefer it. Since I am right-handed, it seems much more natural to reach across my body with my right hand and work the zipper when it's on the left side than to twist my wrist at an odd angle to zip up on the right. I'm quite glad the Helium came that way.
But has anyone else heard of "Men's lefty/Women's righty"? or was the REI salesguy making that up? If he was not making this up, what is the logic of gender-based zipper placement?