Given how much of AD&D was derived from Tolkien, I can understand why they would have magic armor reduced in weight. However, one of 2e’s numerous failings, that I will point out at every opportunity, was in not understanding why it happened in the first place. The entire idea was based on Bilbo’s mithril chain. The armor was light because of the material and construction, not because it was “magic”. Enchanting something doesn’t automatically alter any particular characteristic. If this weight reduction (and subsequent lessened Strength requirement) were valid, all magic items would be reduced in weight compared to their normal counterparts. This is clearly not the case. Tomes remain heavy and bulky, amulets bow to gravity and lie gently on the chest or neck, and potions retain their viscosity. Indeed, imagine the difficulties involved with enchanted arrows, whose efficacy depends on the physics of their flight remaining stable.