Franklin Harris makes an interesting comment concerning an Isaiah variant:
In some cases the Book of Mormon text adds "and," which in Hebrew is represented by a single character "waw," inferring there has been an omission from the present Hebrew text, the addition is confirmed by the Septuagint and the Syriac. Examples are found in Isaiah 3:14 (2 Nephi 13:14), 48:13 (1 Nephi 20:13); 50:9 (2 Nephi 7:9); 51:18 (2 Nephi 8:18). (Franklin S. Harris, Jr., The Book of Mormon: Messages and Evidences, pp. 50-52)
[Quoted by Jeff Lindsay, "Did Joseph Smith Plagiarize from the King James Bible?," Book of Mormon Commentary, [www.jefflindsay.com]]