Referring to the waters of the Red Sea, the printer’s manuscript reads “and they departed hither and thither”. The 1830 typesetter thought that departed was in error and substituted the visually similar verb form parted (“and they parted hither and thither”). We do not have the original manuscript here, but it is possible that it read parted and that Oliver Cowdery miscopied it into 𝓟 as departed. It is also possible that Oliver wrote down departed accidentally in 𝓞. Even so, there is no independent evidence in the manuscripts for adding or omitting an initial unstressed de for words. Potentially there could be mix-ups between the following pairs of verbs (or their forms):
delay lay
delight light
denote note
depress press
But there are no examples of any mix-ups, not even scribal slips, involving these de-initial verbs.
Another possibility is that the reading in 𝓟, departed, is an error for some other de-initial verb. One obvious candidate is the visually similar divided; the word in 𝓞 could have been divided, but Oliver Cowdery misread it as departed when he copied from 𝓞 into 𝓟. In fact, when referring to the parting of waters, the King James Bible uses either verb, part or divide:
The Book of Mormon itself prefers the verb divide in the context of the phrase “hither and thither”:
And the first two examples specifically refer to Moses’s dividing of the Red Sea; thus divided is a possible emendation for departed in Helaman 8:11. Even so, there is no evidence in the history of the Book of Mormon text for mix-ups between the verbs divide and depart.
Another possibility, one consistent with the archaic lexical usage elsewhere in the original Book of Mormon text, is that the reading departed in Helaman 8:11 is actually correct and that it means ‘parted’ or ‘divided’. The Oxford English Dictionary gives ‘to divide or part’ as one of the earliest meanings in English for the verb depart; the first four definitions (listed under section I) provide citations of this obsolete usage, including several that refer to religious subjects (original spellings here retained):
Note how the King James Bible studiously avoids using the verb depart in places where earlier translations of the Bible used that verb with the meaning ‘to divide or part’.
As discussed under Mosiah 19:24 (with respect to the possibility that ceremony is an error for the archaic word sermon, meaning ‘talk, discourse’), the English-language vocabulary of the Book of Mormon appears to date from the 16th and 17th centuries. From that perspective, there is nothing wrong with the use of departed originally in Helaman 8:11. Of course, the 1830 typesetter had no idea that departed could be correct.
The critical text will therefore restore departed in Helaman 8:11, the reading of the earliest extant source (the printer’s manuscript). For the two possible emendations, parted and divided, there is no independent evidence in the history of the Book of Mormon text to support the hypothesis that either of these two verb forms could have been accidentally replaced by departed during the early transmission of the text.
Summary: Restore in Helaman 8:11 the original verb form departed (“and they departed hither and thither”), with the understanding that here departed means ‘parted’ or ‘divided’; such archaic meanings for Book of Mormon words (dating from the 1500s and 1600s) can be found elsewhere in the original text.