Generally the text capitalizes common nouns such as Messiah (but not pronouns or generic nouns such as one or man) that refer to Jesus Christ, even when they could be read as not referring to deity. Here the use of the indefinite article a rather than the definite article the suggests that the noun messiah could be interpreted as common, with the original Hebrew meaning of ‘an anointed one’ (especially a king).
The printed editions (but not the manuscripts) are consistent in using capitalization for such nouns, as in the following two passages:
Also note in the first example the capitalization of the noun savior in the printed editions. There are also five examples of “a Christ” in the Book of Mormon (Jacob 7:9, Alma 30:13, 15, 26, and Helaman 16:18), and in the printed editions all are set with capitalization. Of course, Christ is just the Greek translation of the Hebrew Messiah, so it too can be used as a common noun.
This tradition of capitalizing such nouns is found in the King James Bible (as in Luke 2:11: “for unto you is born this day in the city of David a Savior which is Christ the Lord”).
Summary: Retain the traditional capitalization of common nouns (such as Messiah and Savior) when they refer to Jesus Christ.