This particular group of believers had misread the scriptures, but they were still believers, and sufficiently humble to accept correction. They learned the proper understanding of the scriptures, and accepted them.
Translation: The presence of the phrase “jot nor tittle” shows the influence of the KJV on Joseph’s translation. The jot refers to:
“… the English form of the Greek iota, i.e., the smallest letter of the Greek alphabet. The Hebrew is yod, or y formed like a comma (’). It is used metaphorically to express the minutest thing.” (William Smith. A Dictionary of the Bible.)
A tittle is:
“A point, (Matt. 5:18; Luke 16:17), the minute point or stroke added to some letters of the Hebrew alphabet to distinguish them from others which they resemble; hence, the very least point.” (M.G. Easton. Illustrated Bible Dictionary.)
The reference to the jot might have been part of the plates if it refered to the Hebrew yod. However, the tittle has reference to the pointing of the text for purpose of noting the vowels, a system which was developed after Lehi and his family left Jerusalem. (Emanuel Tov. Textual Criticism of the Hebrew Bible. Fortress Press, Second Revised Edition. 1992, p. 29). Thus the tittle could not have technically been part of their vocabulary. Nevertheless, the concept that the slightest part of the law might not pass away is certainly a sentiment that would have been available, and it is one that Joseph translated into the available idiom that was used for that meaning.