You must have failed in your research efforts to learn that the majority of the changes came from Joseph's own written notes. -- oops
If you don't believe me, go to the church history museum... there's nothing being covered up here.
The current (1981) edition of the Book of Mormon has this notice printed at the bottom of the page opposite 1 Nephi, chapter 1:
Some minor errors in the text have been perpetuated in past editions of the Book of Mormon. This edition contains corrections that seem appropriate to bring the material into conformity with prepublication manuscripts and early editions edited by the Prophet Joseph Smith.
Significant changes
Some Book of Mormon changes were corrections of transcription or printing errors.Changes that would affect the authenticity of the Book of Mormon are limited to:
those that are substantive AND could possibly change the doctrine of the book OR could be used as evidence that the book was written by Joseph Smith.
There are surprisingly few meaningful changes to the Book of Mormon text, and all of them were made by Joseph Smith himself in editions published during his lifetime. These changes include:
"the Son of" added to 1_Ne. 11:18; 1_Ne. 11:21, 1_Ne. 11:32, and 1_Ne. 13:40.
"or out of the waters of baptism" added to 1_Ne. 20:1.
"white" changed to "pure" in 2_Ne. 30:6.
"Benjamin" changed to "Mosiah" in Mosiah 21:28 and Eth. 4:1.
"Words missing in Alma 32:30"[3] Alma 32:30-31
The historical record shows that these changes were made to clarify the meaning of the text, not to alter it.
The authenticity of the Book of Mormon is not affected by the modifications that have been made to its text because the vast majority of those modifications are minor corrections in spelling, punctuation, and grammar. The few significant modifications were made by the Prophet Joseph Smith to clarify the meaning of the text, not to change it. This was his right as translator of the book.