Here's another question. Why is the sodbuster pattern not considered a "peasant knife"? Personally I think it's in the same class if we're making it so broad as to include pieces as vastly different from each other as the Svord and Opinel models. Any of the locking Opinels are not friction folders, so I'd figure that other simple knives like the Mercator K55K and the Douk Douk would be in the same class? I'm perhaps a little confused by the lack of clarity.
Great question.
Best answer I can give is that my categories are arbitrary and capricious.
More seriously, for me the primary distinction is the existence of a back spring and typically separate scales. We went around a bit on the categories in the original thread a month or so ago when I was thinking about the categories to run in the bracket. One part of that discussion centered on whether or not the peanut should be considered a serpentine jack and, related, if there should just be a broad category for all 2 bladed jacks or not. In the end, I sided with a body of mine who, when talking about such things in a different field advised me to pick categories that are useful, not correct. I think your comments about the sodbuster really being a form of peasant's knife is well made and well taken. But at the same time, I think most discussion on this board distinguish between them, at least based on what I've seen. I'm not saying that's right. Just commonplace.