churchistrue wrote:[A] 19th century author mimicking Early Modern English is the most plausible explanation.
Not even this, I think. To me the obvious explanation is that a 19th century author was trying to mimic the King James Version, but failing. The overdone archaism of this incompetently faked dialect then gets it falsely classified, by linguistic methods that are designed for dating natural language, as an English dialect older than King James.
I am not a linguist at all, let alone a specialist in English dialects, so I can't say that this theory really fits whatever Skousen and Carmack have found. I have a highly qualified linguist in my family, however, and as fellow academics we have often talked shop. I have enough of a grasp of how linguistic analysis works to be sure that the theory of falsely dated overdone archaism is an immediately obvious suggestion to raise.
If your position has an immediately obvious apparent weakness but you have a convincing counter-argument, you shout that counter-argument out right away, and pound the table. You don't expect people to overlook an elephant in the room out of respect for your credentials. And so if a really competent linguist had really firm evidence for this Early Modern English Book of Mormon stuff, their second sentence introducing it would be of the form, "We know this is not just falsely dated overdone archaism because X, Y, and Z."
In other words, if there existed a solid rebuttal to the overdone archaism theory, it would have been shoved down my throat by now. It hasn't been, so I doubt it exists.