Here editors have replaced the object form him with the subject form he. The first RLDS edition (in 1874) made this change, but then the 1908 RLDS edition reverted to the him of the printer’s manuscript. The LDS text made the grammatical change in the 1920 edition. From a grammatical perspective, him is perfectly acceptable in colloquial speech and informal writing, while the use of the subject form he is an artificiality promoted not as much by language use as by language prescriptivists. For further discussion of this point, see it’s me and, more generally, me in MerriamWebster’s Dictionary of English Usage.
There are a few other places in the text where the subject complement pronoun has been edited from the object form to the subject form:
The earliest text prefers the subject form of the pronoun in subject complements. One could argue that these few cases of the object form are due to scribal errors or are the result of Joseph Smith’s own dictation. Nonetheless, there is no scribal evidence (such as false starts or immediate corrections) in the manuscripts to support such an interpretation. Nor did the 1830 typesetter ever correct these supposed errors. In other words, there is no evidence in the initial transmission of the text (from Joseph Smith’s dictation to the 1830 edition) that these nonstandard forms were unacceptable. Only in subsequent editions do we find editors consciously correcting the subject complement pronouns. (Yet in some of these cases, the RLDS text has maintained the nonstandard object pronoun in subject complements.) The critical text will, of course, restore the occasional use of the object form in subject complements, when supported by the earliest textual sources. For a complete discussion, including examples of the subject form of the pronoun in subject complements, see subject complement in volume 3.
One interesting aspect of the original text for 2 Nephi 1:27 is that the original use of him provides a contrastive parallelism with the him at the end of the following main clause:
The change to he cancels the phonetic parallelism between the final words of these two lines. A similar parallelism is found in the example from Alma 46:27 (listed above), where the object pronoun us is repeated (“which have dissented from us / yea and even it shall be us”); the 1920 replacement of us with ourselves breaks the word parallelism between those two lines.
Summary: Maintain the object form him as the subject complement pronoun in 2 Nephi 1:27; such usage is common in colloquial English.