The current text of D&C 84:28, speaking of John the Baptist, reads as follows:
For he was baptised while he was yet in his childhood, and was ordained by the angel of God at the time he was eight days old unto this power, to overthrow the kingdom of the Jews, and to make straight the way of the Lord before the face of his people, to prepare them for the coming of the Lord, in whose hand is given all power.
The handwritten original of this revelation, however, reads differently (emphasis added):
For he was baptised while he was yet in the womb and was ordained by the Angel of God at the time he was eight days old . . . (see Joseph Smith Papers: Revelations and Translation—Manuscript Revelation Books, eds. Robin Scott Jensen, Robert J. Woodford, and Steven C. Harper [Salt Lake City: The Church Historian Press, 2009], 276-77).
In the Kirtland Revelation Book (in many respects, a printer’s manuscript for the 1835 edition of the Doctrine and Covenants), the text was changed to the modern reading thereof (ibid., 458-49).
As far as I can ascertain, there has not been much discussion about this variant, and even then, nothing very substantial; indeed, much of what has been written explaining this change is rather superficial. A good example would be Robert J. Woodford’s otherwise masterful PhD dissertation, "The Historical Development of the Doctrine and Covenants" (3 vols.: Brigham Young University, 1974) writes:
Verse 28 in both Manuscript #1 and the Kirtland Revelation Book have John the Baptist baptised while yet in his mother's womb. This is obviously an error, and justifiably changed. (Woodford, p. 1052).
It is understandable why Woodford (and other LDS commentators) would view this as an “error,” in light of the Church’s very negative view of infant baptism, a doctrine in Roman Catholicism and many Reformed and other traditions (see Moroni 8 which castigates the practice of infant baptism; historically, Latter-day Saints have viewed the introduction of this doctrine as evidence of the apostasy of “Orthodox” Christianity), so an individual being baptised in his mother’s womb will be “odd,” to say the very least. However, from my examination of the evidence, there is no possibility that this was a “mistake” in the handwritten original text due to (1) mishearing by a scribe or (2) any issues relating to misspelling, which accounts for most textual variants in ancient and modern texts (see any good introduction on textual criticism of the Bible or Royal Skousen’s multi-volume commentary on textual variants of the Book of Mormon). The change is obviously deliberate, and not a correction of what was originally uttered by Joseph Smith.
What are we to make of John the Baptist being baptised in his womb? From the context, “baptism” here is not metaphorical—just as the ordination of John to the priesthood is a real, not metaphorical event, as with his confirmation by the Holy Spirit, it is to engage in eisegesis to propose anything other than a literal “baptism” in Elizabeth’s womb. Furthermore, if John the Baptist received baptism in an “ordinary” (to Latter-day Saints) manner, why the explication of his reception thereof? The treatment of this verse and its textual history by Woodford et al., is rather superficial and doesn’t really address the real issues and questions arising from it.
All throughout Scripture, God sets a “fixed norm” for his covenant people, but allows for flexibility in extraordinary circumstances. For instance, In 1 Sam 21:6, David was permitted to consume the shewbread (literally: bread of the [divine] presence), notwithstanding the "normative" command that it would only be consumed by the temple priests. Furthermore, we do know that God sanctifies certain people while in the womb of their mother, paralleling John's baptism in Elizabeth's womb. Note a well-known text often cited by Latter-day Saints to support (personal) pre-existence of all people:
Before I formed thee in the belly I knew thee; and before thou camest forth out of the womb I sanctified thee, and ordained thee a prophet unto the nations.
In this text, we learn that God consecrated/sanctified (קדשׁ) Jeremiah and ordained him (נתן [literally, “to give”]) a prophet while he was still gestating in his mother’s womb; its very explication shows that this was an extraordinary event, perhaps warranted by the mass apostasy of the people of his day (for e.g., see Jer 10:10-11, which shows the idolatry of the general populace).
D&C 84:28, even as it now stands, presents John the Baptist receiving the ordinances of the priesthood in an extraordinary manner, speaking of his being ordained (to the Aaronic Priesthood) by an angel at only eight days of age and being confirmed. Furthermore, in v. 27, we learn that he was “filled with the Holy Ghost form his mother’s womb.” Perhaps, in light of the original reading of v. 28, one could plausibly argue that this was the reception of the ordinance of confirmation (cf. Luke 1:41). Perhaps one could argue (and this is just my working thesis), is that God sanctified John the Baptist in the womb to allow for there to be a forerunner, an Elijah-like figure, to prepare for Jesus Christ and his ministry. By consecrating and regeneration a prophet in such an extraordinary manner, even before his birth, would allow for a holy, righteous individual to carry out the Old Testament prophecy of there being one to prepare the way of Yahweh (Isa 40:3), and we know that God, ultimately, will be triumphant, even in the face of opposition (in the case of Jesus’ time, the mass apostasy of the people; cf. the Hebrew parallelism in Gen 50:20, where Joseph of Egypt recognises that God brings out good from evil).
Of course, the above is speculative, but I think in light of the exceptions God allows for, and Himself makes, even within the realm of soteriology, one perhaps could argue that John the Baptist is a break from the “norm” of waiting until the “age of accountability” for the reception of baptism and confirmation. One thing is clear, however, is that LDS commentators on the Doctrine and Covenants have to do a more persuasive job on discussing this change.
If there has been any sustained discussion of this change, I would like to know--one can contact me at irishlds87atgmaildotcom and let me know of the source(s) that go in-depth on this change.