Several early English Bibles and many modern translations including the NKJV clearly, precisely, and accurately identify Jesus Christ as "our God and Saviour" at 2 Peter 1:1. William Tyndale in 1534 and John Rogers in 1537 translated the last part of this verse as "righteousness that cometh of our God and Saviour Jesus Christ." The Great, Whittingham's, Geneva, Bishops', Haak’s 1657 English translation of the Dutch Bible, Wesley's, 1842 Baptist or Bernard's, NKJV, Majority Text Interlinear, and many other translations render it "righteousness of our God and Saviour [or Savior] Jesus Christ." James White maintained that this is the proper translation of the Greek according to the Granville Sharp's rule (King James Only Controversy, p. 268). Granville Sharp (1735-1813) cited 2 Peter 1:1 as his first example “of sentences which fall under the first rule, and are improperly rendered in the English version [KJV]“ (Remarks, p. 20). James D. Price noted that “the Greek grammatical construction here identifies Jesus Christ as God and Savior” (King James Onlyism, p. 323). Concerning this verse in his multi-volume commentary, David Sorenson wrote: “Though it is not quite as evident in English, in the Received Text, the phrase literally reads, ‘the righteousness of our God and Savior Jesus Christ’” (p. 228). Kenneth Wuest asserted: “The expression, ‘God and our Saviour’ is in a construction in the Greek text which demands that we translate, ‘our God and Saviour, Jesus Christ” (In These Last Days, p. 17). John Ankerberg and John Weldon noted that “Greek scholars Dana and Mantley, in their A Manual Grammar of the Greek New Testament, confirm the truth of Sharp’s rule, and then explain: ‘Second Peter 1:1 … means that Jesus is our God and Savior” (Facts On Jehovah’s Witnesses, p. 24). In his commentary on 1 and 2 Peter, Gordon Clark translated the phrase as “of our God and Savior, Jesus Christ” (New Heavens, New Earth, p. 170). Clark noted: “Other references to ‘our Lord and Savior Jesus Christ’ do not diminish the deity asserted here in 1:1” (p. 171).
Surprisingly, the 1611 edition of the KJV has a comma after God at 2 Peter 1:1 [God, and our Saviour Jesus Christ], and that comma seems to have remained in most KJV editions printed up to the 1769 Oxford edition. The 1743 Cambridge and 1760 Cambridge editions had removed it before the 1769. Even the first KJV edition printed in America in 1782 and KJV editions printed at Oxford in 1788 and in 1795 still have a comma after God at 2 Peter 1:1. How does this comma in KJV editions up to the 1769 Oxford affect the understanding and interpretation of this verse? Concerning this verse in his 1633 commentary on 2 Peter, Thomas Adams observed: “Some read these words by disjoining them; of God, and of our Saviour,“ which would seem to refer to the rendering in the 1611.
At 2 Peter 1:1, the 2005 Cambridge edition of the KJV has this note taken from the standard 1762 Cambridge edition: “Gr. of our God and Saviour.” KJV editions printed at Oxford in 1810, 1821, 1835, 1857, 1865, 1868, and 1885, and at Cambridge in 1769, 1844, 1872, and 1887 also have this same note. Granville Sharp observed: “In the margin of our present version the proper reading is ‘of our God and Saviour,‘ manifestly referring both titles to one person” (Remarks, p. 22). James Scholefield maintained that this verse has “the same construction as in verse 11” where it was rendered in the KJV as “of our Lord and Saviour Jesus Christ” (Hints, p. 157). A. T. Robertson wrote: “In 2 Peter 1:11 and 3:18, the pronoun ’our’ comes after ’Lord,’ but that makes no difference in the idiom. It is ’our Lord and Saviour,’ and it is so translated in the English versions. But we have precisely the same idiom in 2 Peter 1:1, ’our God and Saviour Jesus Christ’” (The Minister, p. 63). Robertson asserted: “The idiom compels the translation, ’our God and Saviour Jesus Christ” (p. 64). Concerning 2 Peter 1:1, Ralph Wardlaw noted in 1815: “An instance of construction, in every respect the same, occurs at the eleventh verse of this same chapter” (Discourses, p. 75). Wardlaw asserted: “It is just as improper to render the words in the first verse, ‘through the righteousness of God and our Saviour Jesus Christ,‘ (unless the appellations ‘God and our Saviour’ be understood as both connecting with ‘Jesus Christ’) as it would be to render those in this verse [1:11] ‘in the kingdom of the Lord and our Saviour Jesus Christ’” (p. 76). John Dagg indicated that the rendering in our common English version at 2 Peter 1:1 should be emended to “the righteousness of our God and Saviour, Jesus Christ” (Manual of Theology, pp. 183-184). Timothy Dwight (1752-1817) wrote: “According to the original, of our God and Saviour, Jesus Christ” (Theology Explained, I, p. 525).
First, my KJB does not have this comma.
Second, I hardly think this discredits the original 1611 KJB. You would have to prove that the translators intentionally inserted this comma to give 2 Pet 1:1 a different meaning. Can you do that?
It is very likely that this was a typographical error that was copied for some time. Printing was very primitive in 1611, and typos were common. Thousands of copies would be sold and distributed, others would copy these editions. The Bible is a massive book, sometimes errors were not spotted until many years later. In the mean time, thousands of copies with these typos were printed and often copied by others. The fact that this error was spotted and corrected shows the original text was without corruption.
And this is the real issue between the KJB and the MVs, the original source text. As I have said, the TR has nearly 3000 more words in the original Greek than the CT. This cannot be blamed on a "typo". Entire verses and even passages are either added in the TR, or omitted in the CT according to your perspective. I believe the CT omits scripture.
The omitted "a" in John 4:24 is another matter altogether. In our modern age with computers, scripture can be checked in seconds (or minutes at most) for errors. This difference was known long ago, so there is no excuse other than the NKJV intentionally selected a translation that conforms to the MVs and departs from the KJB.