Latter-day Saint scholars Richard D. Draper et al. observe that Cain's "mark is not the same as the curse, which carried multiple penalties."
Richard D. Draper, S. Kent Brown, and Michael D. Rhodes. The Pearl of Great Price: A Verse-by-Verse Commentary (electronic edition) (Salt Lake City, UT: Deseret Book, 2005), 73
I the Lord set a mark upon Cain: The second protective aspect is the mark that would visually remind any avenger of God's decree about seven lives for the life of Cain. This mark is not the same as the curse, which carried multiple penalties (see Moses 5:36–37, 41).
Draper et al. are commenting on Moses 5:40, which is identical to Genesis 4:15.