I’ve spent a lot of time trying to figure out the JST, but in this BoM year the thought occurred to me that I’ve never really spent much time looking at how the BOM modifies biblical quotation text. So to dip my toes in this I copied Isaiah 2 into a Word document, made a new version, then copied in 2 Nephi 12, and then ran a comparison. I found the results interesting, so thought I’d share just a few examples of what I found here. Deletions will be italicized, additions in bold.
[2] And it shall come to pass in the last days, that when the mountain of the Lord’s house shall be established in the top of the mountains, and shall be exalted above the hills, and all nations shall flow unto it.
The change from “that” to “when” makes the subordinate clause introduced by the conjunction “that” specifically a temporal clause. In the Bible the temple being established in the last days was the point; in the BoM, the temple being established in the last days is a circumstantial given, and the point is what follows.
[5] O house of Jacob, come ye and let us walk in the light of the Lord; yea, come, for ye have all gone astray, every one to his wicked ways.
Joseph adds text from Isaiah 53:6, but changing “his own way” to “his wicked ways.”
[6] Therefore, O Lord, thou hast forsaken thy people, the house of Jacob, because they be replenished from the east, and are hearken unto soothsayers like the Philistines, and they please themselves in the children of strangers.
The insertion of “O Lord” is simply for clarity. The NET makes exactly the same change. The BoM also corrects an error in the KJV here. The KJV portrays the people themselves as soothsayers, but that is incorrect. The text literally says “they are full from the east,” meaning the soothsayers came from the east., and the people are giving them heed; they are not themselves the soothsayers as the KJV wrongly suggests.
[9] And the mean man boweth not down, and the great man humbleth himself not, therefore, forgive them him not.
The BoM takes the bowing and humbling oneself as it relates to Yahweh, so it suggests they were not doing that, which is why they were punished. But in fact the bowing was to other gods, which is why humbling themselves before such gods was worthy of judgment.
That is just a taste to give yuou a sensee of the type and extent of the variations from the KJV introduced in the BoM KJV quotations.
By Common Consent, a Mormon Blog 
I was just listening to the BYU roundtable on this subject. ( https://www.youtube.com/watch?v=Z2Y434NFcgc ) They do a great job showing how the Isaiah texts are being played with by the BoM writers as they liken scripture to themselves. Thanks for this, really fascinating!
“But in fact the bowing was to other gods, which is why humbling themselves before such gods was worthy of judgment.”
That’s not mutually exclusive though, is it? If you’re bowing before another God instead of the Lord, you’re not submitting to God. And in the context of an ancient society, it’s not as if the verse was aimed at a bunch of people who refused to bow before any God.
BTW, Royal Skousen’s book on the KJV quotations is coming out, which I’m looking forward to (my copy hasn’t come yet.
[10] [INSERT] O ye wicked ones, [/INSERT] enter into the rock, and hide thee in the dust, for the fear of the Lord and [DELETE] for [DELETE] the glory of his majesty [INSERT] shall smite thee [/INSERT].
(I’m at work now and can’t seem to use fonts, so I’ve used bracketed tags to mark inserts and deletions. Also, my apologies for some typos in the OP; I recently had eye surgery and my vision’s a little blurry.)
The first insertion, “O ye wicked ones,” is intended to make quite clear that the people described in the prior verse were in fact wicked, which is not clear in the KJV. The addition of “shall smite thee” at the end is to make explicit the import of the expression “the glory of his majesty.”
[11] [INSERT] And it shall come to pass that [/INSERT] the lofty looks of man shall be humbled, and the haughtiness of men shall be bowed down, and the Lord alone shall be exalted in that day.
The insertion “and it shall come to pass that” makes it clear that this will happen in the future, which should already be apparent by the tense of the verbs.
I don’t think you can capture everything that is going on without paying attention to what happens to what was italicized in the KJV
Jacob H, yes, italics were definitely an influence.
Grant Hardy has a bunch of this in the Maxwell Edition version of the BoM he edited. Thanks for sharing this – really interesting stuff.
For me “The Vision of All: Twenty-five Lectures on Isaiah in Nephi’s Record” by Joseph Spencer really changed the way I look at the Isaiah chapters in the Book or Mormon.