A quick few things for those who've taken interest in the thread, but first, thanks again for taking the time out, Ferne (Far-off Saint, indeed). We're very appreciative that you two care as much about clear delivery of context as you do the grammar being correct.
Looking at the alternate language terms for the mobs gives a lot of clues; in fact, soulkin was the only one that didn't outright explain itself when looking. Fun Fact: The German version uses psychological fear terms as eluder names, so "Seedkin Eluder" becomes "Dendrophobia," the fear of plants. Anyway, full list:
Ashkin - Undead (Something dies, you burn it, it's ash. BUT IT'S BACK!)
Beastkin - Mammals (Beasts)
Cloudkin - Avians ("The Winged")
Forgekin - Machinery (Forged by hand)
Scalekin - Reptiles (Lizards)
Seedkin - Plants (Born of Seed; cannot...unimagine...goobbue birth...)
Soulkin - Cursed (We now know why they're cursed; an invasive secondary force)
Spoken - Bipedal Sentients (Not ogres; "GRRUGGG" is not sentience.)
Vilekin - Insects (NOT "pests," specifically insects)
Voidsent - Not of Eorzea (Great post on this a few threads back, "void vs. Void")
Wavekin - Aquaans (Obvious, but electrocute it just to be sure.)
I hope to have all of this covered and reorganized in the Wiki soon, but pretty much every facet of it is undergoing huge changes, so we'll see where it goes. @.@
Answers to questions above:
Why isn't this information covered elsewhere?
From what I've gathered from posts so far, it was originally planned that all sorts of new information would be added to the Lodestone and official FFXIV website shortly after a successful launch (hint: launch was not successful.) and ever since then they've had to redirect their efforts. It may take some time.
Can another kindred become a Soulkin?
Another creature can become bound to an object, sure, but I don't think it changes their taxonomy until the entire species conforms to that specific trait. A Spriggan's relationship to the rock it derives power from is much more concrete.
That said, I'd love to see more information on the Ask the Devs! and official sources, but we do have to understand that the actual game should be ready before the guides to it are created, otherwise it'd be a nightmare going back and changing them.
Try not to forget that our dear localization ahriman and opo-opo can't just add things to the game or Lodestone, they localize existing information so that players who don't use the origin language version can still enjoy it - and from what I hear, the English version is so stylized and intricate that it's actually chosen over some players' native languages (Now there's a compliment!). Therefore, getting more information into the official sources would need to be asked of more than just Ferne and Eme, but it has to be passed to the highest echelons for universal implementation before they can get to localizing it for us.