some more Vernaculars
Also, Chalcy, Rhythnorian (I think), and (of course) Tyrean and Chaeronian (Ventrian remains pretty much High Choleic, with only 200 years of drift, but Tyr and Chaeronia have had huge Andarian influences on the language). Some more: Picantean, Ostian (closely related to current Orsinian). Conceivably, Tyrrulean, Picardian, Ashregi, Avereth (Avereth being the most likely of the Dawnish and Northern languages, since they aren't theocrats). And, lately, Gaetani.

I would agree that use of foriegn vernaculars are suspect, although not that uncommon (I'd add the Arcadians to the list of vernacular users). Use of Tympanian vernacular is probably less suspect, although disdained. I suspect a lot of Bethelion students experiment with the use of Tyrean instead of High Choleic in their spells, and need to be smacked out of it by their masters.

Using foreign vernaculars probably causes fewer problems than using Tympanian vernaculars. The ambiguities between Tyrean and High Choleic probably cause casting problems if you aren't careful (or so I'd imagine).

RE: Vernacular
It wouldn't surprise me a bit, actually, if there were a good bit of Ulderlindener vernacular floating about in the spells coming out of St. Kevin of the Apples, or in the works of the early Melians. I could also see the Savacion combat lores making ample use of Andarean phrases, rather than Cholaeic ones.

(RE: Chalcy Elementalism)

It’s just that objections to date so far haven’t focussed on the issue of language.

Well, they might have, really. I mean, history does record that conservative magi find that Chalcy stuff all terribly dubious and all, but it never goes into precisely what the arguments against it were or are. The use of foreign vernacular might well have been one of the issues that was/is considered a Very Big Deal.

In Scriba Fusca's wiki entry--or maybe it was in the wiki for her book, I can't remember--I seem to recall specifying that one of the advanced editions has entire sections written in Tyrulean, and implying that this had been a pretty ballsy thing for her to have done. Then, that's Tyrulean, which I think would certainly be a vernacular that would cause raised eyebrows, even if writing in other vernaculars were considered overall Okay.

Oh, and other vernaculers - there's also whatever they speak in the Skulstorren, which I'm guessing is the one that the Arcadians are wont to use.

Lake District and Vernacular
Do Lake District folk speak Skulstoren or Ulderlinden.

Other vernaculars: Novalindener, and whatever they speak up the West. Also, the language of the Shru Kephis.

On languages, does everyone else imagine that Skulstoren, Ulderlinden, Novalinden and West are closely related languages?

Also, I imagine the Castrians use some Westmarcher in their spells, since living among the people is very much their point.