Dr. Awkward said:
Indeed.
How does a skeleton talk without any talking apparatus? It's like asking it to dance with no legs.
Oh, sorry, but weren't we talking magic and magical effects in a fantasy world ? How do Shadows float btw ? Or Wraiths pass through walls - or how does a Ghost wail, if he is incorporeal and certainly missing any physcial vocal chords and thorax ?
Because its a world that is kept ticking by slightly different rules, laws and universal field theories than the real one perhaps ?
If I can accept a divine being channeling power through its mortal servants to speak with corpses rather frequently, but flinch at the lack of a thorax to faciliate communication, something smells fishy....
The question IMHO ought to be - is the lack of a voicebox/thorax/throat too much an impedienment for a spell of the 3rd level to overcome or would it be unbalacing to the game if allowed ?
In all honesty - I don't see all that many problems with magic conjuring up a disembodied voice to speak up for the dead body about information the caster is arguably extracting from the cadaverous remains of the deceased ( strikes me - YMMV - as slightly more difficult then a mere "ghost sound" parlour trick to convey the information )....
So game-effect balancing looks allright from here.
As for the more difficult question of the rules for "Speak with Dead" making sense - taking the WotC email's text verbatim will lead to some massive adjucating problems (not that WotC ever really worried about those) , because if applied universally, a plethora of wounds will preclude the use of the spell.
E.g. having your throat cut (happens to guards all too often ), torn out (always a favourite way of dispatching by large predators - wolves, lions etc. ), smashed, getting decapitated (be it by bite, blow, blade or guillotine) or even simply having you jaws smashed by some wicked blows. Things like a smashed chest, lungs punctured by bundles of arrows etc etc etc
ad nauseam might prove pretty much of an obstacle, too (no air pressure form those lungs) - from a medical/physical point of view. But D&D V3.5. is not - or rather "shouldn't be" - a pathology class, right ? Again YMMV.
D&D v3.5 does not support a "hit-location" and "type-of-wound" system, so any description of a wound is an arbitary, unsupported by the rules act by a GM (not that there is anything wrong with that ). But what
precisely then makes a corpse a " mostly intact" one ? Personally, as long as the limbs are all there and accounted for, and the body has not been ground to dust or splinters, we have a candidate for "Speak with Dead". Victims of headhunters, things swallowed by dragons, dissolved by green slime, gelantinous cubes, puddings of any colour, taste or size etc need not apply. Or basically, if you can animate it, you can interrogate and cross-examine it.
Besides deep freezing someone (and except for some unlucky alpine tourists, that happens very rarely, mostly to polar explorers ), there is hardly any way to preserve a corpse "intact" (well, do the maggots and other decaying symptoms count - and what knowledge is lost in what way by that , if one wants to stick to high percentage "intact" corpses ?) over any amount of time. Mummies - it helps taking a good look at mummification processes here - are not really "intact" anymore, once they are ready for the afterlife. Ritual disembowelment, removal of the brain and several other procedures do not really keep a corpse complete.... Other real life mummified corpses like those created through exposure to a dry cold (e.g. Incan mummies, or the more or less famous ice age corpse "Oetzi") are usually pretty much damaged by the environment, including massive shrinking and distortion, abrasion from wind and particles... the works. Intact ?
As for "Moorleichen" corpses, preserved through immersion in oxygen-poor bogs (which keeps them from rotting - but at the same time tans them much like hide is tanned to become leather), the same phenomenon applies - and I sincerly wonder how (and why, in a fantasy campaign ) one would get access to one of those in the first place underneath several feet of peat and bog.
The main troubling question with "Speak with Dead" is - how much does it ruin the plot, if the players cast the spell on a key corpse and ask precisely the right questions ? And whether they do not deserve the information if they do everything right...
Keeping such knowledge from players on a technicality like "oh, no thorax, sorry guys, your spell fails" seems like a cheap cop-out to me. If it ruins your plot, be vague, distort things by the corpses prejudices, lack of information and point of view. As noted in the spell's description - be brief, cryptic and repetitive. Besides, the corpse does usually get a Will-save... which the GM is free to "fudge", in the interest of keeping the plot interesting and fun. YMMV.
As a short-cut solution - IMC, villains commonly take the head as a trophy, if they are afraid someone may spill the beans (and drop it off some miles away, if the PCs then find and recover it, more power to them ). Oftentimes though , that gesture alone is clue enough to help the players along and in a way, verify their suspicions.