Hrm... I think I am still a bit confused over what makes demons tendenced to generally (though not always) obtain mindset that might fit the general perception of evil, and gods one that might fit the general perception of good. Their instincts, which you referred to? Something about how the seeds were made by the respective spirits? If their drive makes them more likely to do things of a specific kind, then the drive probably has some kind of preset?

Do mortals get their seeds of the opposite alignment expunged when they get turned into demons or angels?

Why do plants not qualify as mortals? I recall their souls are typically more placid, and that in this world a plant-soul can reach over multiple individual plants (though wouldn't it make them one person, rather than not mortal? what about colonial animals, especially the lesser ones?). Real-life plants typically communicate chemically (and while some of them work together, even across species, they more commonly try to kill one another off). The changes of a plant's chemical composition can also be insanely fast.

@Nessa: Your turn in the collab?