A quick check of the AD&D Monster Manual shows the shadow and spectre (as well as wraith) having a chilling touch, described as supernatural cold. I never said that an incorporeal creature couldn't supernaturally affect a corporeal one; I just said that all HP damage is described in a manner that's consistent with physical injury. Chilling touch makes sense as dealing cold damage, at least as much as Cone of Cold does.
I have to imagine it's similar logic to a sneak attack; failing the save means you're allowing the 10% of non-illusory energy to hit you in the worst possible way. Honestly, though, if you accept psychic damage as being physical damage to the body (albeit caused by the mind), then we may not be so far apart on this than I had originally thought. Most people seem to pitch psychic damage as an entirely non-physical phenomenon, with no signs on the body whatsoever.
I won't argue about the design issues inherent with non-damaging spells. I'm a big fan of Pathfinder's decision to make Turn Undead into a positive energy wave damage effect, for example.
Well, I still think that Gygax was perfectly justified in, and he certainly hit common usage squarely, when he described hit points as a combination of things and implied that 'hit' and 'miss' are simply conventions, not literal rigid narrative. It isn't all that easy to come up with ANY really consistent single interpretation of D&D rules, and I don't think it is worth doing, really. Saying you can only play with people who imagine it a certain way definitely strikes me as quite rigid, and odd for play of a game of pure imagination.
So, in the end, IMHO all 4e did was be more consistent about utilizing hit points as 'measure of defeat' rather than being all over the map in terms of what they're doing in any given situation. That is greatly helped by a consistent set of mechanics. Much easier to construct an interesting narrative with this sort of wiggle room, IMHO.