It is obvious that the or- clause here includes within its scope the main clause “I ordain you to be a teacher”. However, beginning with the 1830 edition, all printed editions have had parentheses placed around only the if- clause:
Quite clearly, the one ordaining does not say “I ordain you to be a priest / I ordain you to be a teacher”.
This punctuation difficulty is apparently mentioned by Paul Cheesman on page 163 of The Keystone of Mormonism: Little Known Truths about the Book of Mormon (Salt Lake City, Utah: Deseret Book, 1973). Cheesman refers to this verse as having a problem with punctuation. Over the years Daniel Ludlow has advocated emending the punctuation for this passage (personal communication). Finally, the 2004 Doubleday version of the Book of Mormon made the correction (the text for that edition was provided by the LDS Church).
Summary: Extend the scope of the parenthetical insertion in Moroni 3:3 to include “I ordain you to be a teacher”; the complete or- clause (“or if he be a teacher / I ordain you to be a teacher”) should be set off by dashes or parentheses.