I think the mix your labor approach shows a sign of ownership. It’s not completely necessary, but it provides boundaries to be rationalized, meaning, comprehended by others. As nirgrahamUK mentioned just spitting there can show a sign of ownership. By sign of ownership what is being pronounced is presence. This rids the notions of just by viewing with ones eyes then all that is seen is the viewers. The viewer didn’t work for any of that land other than what effort it takes to look with ones eyes. That leads into all kinds of hypotheticals. Who saw what and how much kind of argumentation and we can’t get into everybody’s eyes. So patterns that are distinguishable and significant enough for others to honor such claims focus on signs and boundaries. These signs are also known as evidence. Now as I said with nirgrahamUK, the farmer could plow the spit away, knowingly or unknowningly, and the spitter has first claim rights. Yet, the farmer shows better evidence by the plow marks. Evidence helps resolve disputes. So evidence is not needed if there is no dispute. But once a dispute begins, then reasonable patterns need to be distinguishable enough for the farmer, spitter, and/or a grand jury if necessary.
So basically the “mix your labor” is another way of creating evidence of ownership. All can see the individual’s impact upon nature. It helps resolve disputes. Also helps make boundaries or I could claim everything that is not occupied around the world even though I’ve never even been to any of these unoccupied places aside from ever seeing them. A society that would recognize that claim would be not only silly, but be one dominated by making ownership claims instead of also recognizing that life is not just about claiming ownership. We do partake in other events in our lives.
As to the moral and ownership principles you mentioned in the rest of your post. I liked them a lot and that is another way to show ownership. [Y]