(I'm fairly convinced that a language like the hypothetical Tenebric would have at least four ways to mark that uncertainty on the predicate itself, so that's kind of all too appropriate.)
Heh. You bet!But you propably have experiences with "hedging"
Yeah, that's somewhat better. (And the idea that the Devils or the Yugoloths would try to create a Fiendish lingua franca for all fiends, leading to the greatest epic fail in the history of language planning makes nine kinds of sense.)Incidentally, you may like what the fanmade conversion of Planescape to 3.5 on planewalker.com did: it stated that the Archons, Guardinals and Eladrin all used to have languages on their own, but over millenia of cooperation these fused into Celestial. Archon, Elysian and Eladrin are still spoken by some beings, but are generally not used anymore.
(planewalker also invented Fiendish as a failed experiment of a lingua franca of the fiendish races.)
Plus, the demons are more like three groups (obyrith, tanar'ri, loumara) at the least that hate each other. And the tanar'ri also kind of hate each other. And then we didn't even touch upon all the other weird folks living in the Abyss. I think it won't surprise you much that I'm very fond of the Abrians.On the other hand, the Abyss is mostly inhabited by a single group of beings, even if it is as diverse as demons. Shadow lacks such a group.
On the athach's third hand, according to the Spelljammer setting Common is spoken on pretty much any world, even those that never were touched by human hands, so that is not exactly a counter argument.