Jacobean English was pretty much the form of English most English-speaking Protestants would have been familiar with, so that was effectively the language of the day when it came to religious material.
The problem with this is that the BOM does not reflect proper usage of the time, either in its high form (as in religious readings) in Joseph's own time or earlier. The frequent confusion of pronouns, for instance, casts it quite clearly as a poorly done imitation of the KJV, with very little regard for how the language of that era was used. So whether or not it sounds non-standard to us today doesn't really matter; the point is it wouldn't have passed muster
then, either.
From
wiki:
2 Nephi 1:30–32, Lehi speaks to Zoram: "And now, Zoram, I speak unto
you: Behold,
thou art the servant of Laban...if
ye shall keep the commandments of the Lord, the Lord hath consecrated this land for the security of
thy seed with the seed of my son."
You/ye are plural pronouns and
thou/thy are singular pronouns, but the text switches back and forth between them.
+++
LDS apologists have tried to address some of the many errors that appear in the BOM, even claiming that
they are evidence in favor of the text rather than against it, but generally speaking the examples they use are not of the same type as the above. For instance, if you click the link you'll read about how it was once acceptable to write “The wars and weapons are now altered from them days”, rather than "those days", as we would today. Yes, that sounds like an error to the modern, educated ear, but that's a confusion between the third person accusative pronoun (accusative form of 'they') and a demonstrative pronoun ('those'). Those two types of pronouns do not form a cohesive paradigm:
I > me; you > you; he > him; she > her; they > them; we > us; etc.
That's a paradigm. If you know the language, you know this, even if you've never seen it laid out in a systematic fashion.
Whereas demonstrative pronouns are just...demonstrative pronouns. They do vary by distance from the speaker (here/there), and whether they're used with singular and uncountable nouns (this/that) or plural and countable nouns (these/those), but they are not inflected as non-demonstrative pronouns are, which makes the confusion between them a lot less damning than the kinds of examples from the BOM such as the above (as that particular confusion between singular and plural would not have been characteristic of Early Modern English, when those pronouns were still in common use; by Joseph Smith's time, however, they had mostly fallen out of use outside of religious readings, which explains why they would be found in the BOM as they are, since they fell out of use beginning in the early 17th century and were basically gone about 1800 -- Joseph, if he was as uneducated as LDS propaganda likes to say he was, would not have known how to use them correctly, but certainly the Almighty would have).
