The 1830 typesetter changed “he sent out through all the land” to “he sent out throughout all the land”, thus creating in essence a double out. The 1908 RLDS edition restored the earliest extant text, the reading in 𝓟. A more consistent emendation for the 1830 edition would have been to change the text to simply read “he sent throughout the land”. There are numerous examples in the text of throughout occurring with land (54 times), but in no case does out occur with throughout (except here in Mosiah 29:1 as introduced in the 1830 edition). But there is one case where “through the land” appears to have the meaning ‘throughout the land’:
There is also evidence in the text that the out of throughout has sometimes been dropped:
It is therefore possible that the case of “through the land” in Mosiah 29:43 is an error for “throughout the land”.
The Oxford English Dictionary shows, however, that through can mean ‘throughout’, as in the following examples (see definition 3 under through as well as the reference to that definition under throughout):
Thus the original occurrences of through in Mosiah 29:1 and Mosiah 29:43 are possible and will therefore be maintained in the critical text.
Summary: Restore the original “through all the land” in Mosiah 29:1; the throughout is unnecessary since this phrase is already preceded by out; also maintain the occurrence of “through the land” in Mosiah 29:43 since such usage can be found in the history of the English language.