Inspired by this question on World Building, I'm curious if the bonus stacking rules from various editions of D&D have ever had in-world justifications.
From what I've found, there's basically been two types of rules:
- Bonuses of the same type don't stack (except for some edition-specific named exceptions): D&D 3e,3.5,4e; PF 1e,2e
- Everything stacks, unless the source specifically specifies otherwise (and many things specify otherwise): OD&D, AD&D, D&D 5e
There's generally good mechanical reasons for the first kind, and thematic reasons for the second, but I've never actually seen an in-world justification for any of it. Has any official rules source (not author commentary) ever explained what characters think about why bracers of defense/armor don't stack with mundane armor, but a ring of protection does? Or why three different spells have overlapping but not stacking effects? Or do they just say "it's magic, it doesn't have to make sense"?