Actually, I think Left-Zip sleeping bags is mostly a convention for men’s bags. If you look at women’s bags (ex Nemo Riff, Nemo Disco, Big Agnes Daisy Mae 15) they are RH zippers. And this has been the convention for a long time because it allows a couple to zip together a men’s and women’s bag.
Jeff, not sure why you addressed your comments to me. If you’d read carefully you’d have seen I was addressing Todd T’s remarks. I understand why bags are LH or RH. They’ve been that way since I started backpacking 50 years ago. I just don’t get why it’s a problem with the way a tent is zipped… at least it’s not for me. Just not a mountain I’m going to die on. But then I came of age in the era of front entry A-frame tents where your friggin sleeping bag zipper didn’t matter. Dan D did a good job of explaining his reasoning. But not all of us are ever going to be pleased. I get it.