He quotes and paraphrases other writers, collects and includes whole texts by other authors, contributes running commentary, and also writes his own narrative.

[5] In his "sixteenth year," being young but "large in stature", Mormon "was appointed by the people of Nephi" to be the leader of their armies,[6] and fought against the Lamanites in many battles thereafter.

[10] However, about thirteen years later, Mormon decided to return as commander of the Nephite armies as they were being badly beaten by the Lamanites.

[12] As the last prophet and keeper of the record, Moroni is said to have become the angel or messenger who revealed the location of the golden plates to Joseph Smith in 1823.

Additionally, Helaman 12 contains a long digression from Mormon where he explicitly states that people tend to become rebellious, causing God to respond with punishment until they repent.

Lacking more information about Nephite and Lamanite history, readers are left to come to a similar conclusion as Mormon based on the evidence he presents.