The mixed nature of the Book of Mormon prose is quite a poser for Mormons, it seems to me. The claim is that Smith could not possibly have produced these utterances because they are in a dialect that was unfamiliar to him. If that claim were right, it would perhaps get Smith off the hook for being author, but it's pretty baffling what kind of "translation by the gift and power of God" might produce such a weird hybrid dialect, with some Early Modern features—yet by no means all—and a lot of thoroughly 19th-century phrases and words with very little if any trace of Early Modern spelling or distinctive lexicon. I mean, if God wants an Early Modern translation—or a 19th-century one—then why not make a proper job of it one way or the other? If the procedure was to let Smith's 19th-century mind loosely select familiar vocabulary to express the revealed meanings, why go all tight in constraining him to use unfamiliar grammar?
Even if the seemingly lousy grammar of the Book of Mormon is pristine EModE grammar, the upshot is rather a confirmation than a contradiction of the Nevermo impression that the Book of Mormon language is ridiculous. One can say that God must just have selected a weird English style for inscrutable reasons, but such a hodgepodge of grammar and vocabulary from wildly different eras seems so unlikely for God that I think one is forced to look again—and look harder—at whether the hodgepodge might have been the work of a less divinely gifted writer.
(I've actually thought of a possible reason why God might have ordained such an oddball translation: maybe the degenerate Mayanized Hebrew of the Nephite original text is somehow brilliantly represented by scrambled English. I've seen translations of Lewis Carroll's nonsense poem "Jabberwocky" into German and French that do a good job of rendering the feeling of the wacky English into differently but analogously wacky German and French. Maybe God was doing something like that, and maybe it was even important because it conveyed the imperfect way in which the Nephites managed to preserve their Hebrew heritage. Or something. I thought it wasn't a bad Mormon spin. But I've suggested it both on Mormon Dialogue & Discussion Board and on Jeff Lindsay's "Mormanity" blog, and nobody seemed to embrace it. I must be missing some nuance of appeal to Mormon thinking. Or maybe it's just the old et dona ferentes, that they fear the anti-Mormons even when we bring gifts because the gifts might somehow be sneaky Trojan horses.)
Leaving the explanation of why God would use EModE grammar with 19th-century vocabulary as a challenge to be faced another day, the Carmack-Skousen approach seems to be to keep insisting that there is no way Joseph Smith's brain could have formulated utterances using EModE grammar. Their argument seems to be a pure appeal to the authority of academic linguistics: linguistics tells us, beyond the possibility of rebuttal by unqualified non-linguists, that human language just works this way. People are helpless slaves to their own native dialects and utterly unable to think outside them; Chomsky said so, so there.
But that's obvious nonsense. It's perfectly true that when we casually speak in our native dialects we follow all kinds of rules without conscious awareness, but this is like the way we breathe in and out all day long without thinking of breathing. We can all hold our breaths, or deliberately breathe deeply or shallowly, softly or heavily, whenever we want. In the same way we can all adopt new kinds of grammar whenever we consciously try. It only takes quite a little bit of practice to speak at length in fluent Pig Latin or Yoda-Speak. If you try it, succeed you will. And we can all learn entirely new languages, perhaps not with full native fluency but certainly with enough consistency to be recognizable. I speak fluent bad German.
So Smith could certainly have written outside his own native 19th century dialect, and also outside the older dialects that he might actually have known. What he probably couldn't have done, though, would have been to imitate any specific unfamiliar dialect accurately. That's the point of linguistics that I think Skousen and Carmack have right. If we gave Joseph Smith the task of imitating Early Modern English, no doubt he'd fail catastrophically.
But let's unpack that a bit. Just how would Smith have failed, if he had deliberately tried to write in EModE grammar? How would we have been able to tell that he'd failed?
It's quite unlikely that we'd be able to show that what he had written was completely incompatible with any actual English dialect that was ever spoken anywhere. It's very hard to say that this or that form of utterance was never used in any given time frame, because we don't have large enough corpuses of surviving texts and transcripts to be sure that no-one ever said anything like that. Smith was a native speaker of English and he knew the King James Bible well, probably along with a number of other books that were old in his day, so whatever he produced would be sure to be old-fashioned-English-y enough that it didn't fall entirely outside the continuum of all English dialects.
Moreover the range of what "Early Modern English" exactly was is broad, like any dialect; anything written within a century or so would have to be counted as valid. It might be easy to show that Smith's fake EModE was no typical form of real EModE, but it would be hard to prove that it was nothing that anyone within the EModE era and geographical range could have possibly uttered.
So how could we identify Smith's failure to write like a real EModE speaker?
What we would surely be able to do, if Joseph Smith had ever deliberately tried to fake EModE grammar, would be to find a bunch of things that he said that were rare in the EModE era but much more common in some later or earlier time frame. And so that's how we'd catch him, not by proving that no EModE speaker could ever have uttered such things, because you can never prove that, but by showing that what Smith had produced couldn't reasonably be identified as EModE because it was much more likely to be something earlier or later.
So that's how Carmack and Skousen are right that Joseph Smith could not possibly have pulled off a deliberate imitation of EModE grammar over the length of the Book of Mormon. If he had tried, their kind of analysis could have exposed his failure ...
... in exactly the same way that it has in fact exposed his failure to imitate the grammar of the King James Bible.