Is the Book of Mormon in English as authentic as in the original, or is Joseph Smith's translation imperfect? It is commonly held in religion that the authenticity and authority of Scripture is highest in its original text, since human translators can introduce errors and misunderstandings not present originally.
However, in the case of the Book of Mormon, the translation is a bit unique given that:

We don't have a copy of the original Reformed Egyptian
Joseph Smith made his translation not by his own linguistic knowledge, but with divine aid and under direct instruction from an angel (who presumably is not subject to the ordinary flaws of human translators)

Given this, does the English text Book of Mormon have just as much authority as, say, the Greek text of Matthew's Gospel or the Hebrew text of Genesis?  Or does Joseph Smith's translation have the same ordinary flaws we would expect from any translation of original Scripture?
Does the English text Book of Mormon have just as much authority as, say, the Greek text of Matthew's Gospel ?


The New Testament part of the Holy Bible, that is to say the collection of volumes contained in, for example, the Authorised Version, from Matthew to Revelation, is compiled from thousands of manuscripts, either partial, fragmented or (rarely) complete ; also from many tens of thousands of Patristic Citations (Dean John Burgon collated over 96,000) ; also  from Lectionary references, similar to the more modern 'Book of Common Prayer' ; and from the 'Versions' that is to say the translations of the apostles' words into Syriac, Coptic, Latin and other languages.
On the other hand, the Book of Mormon is from a single anecdotal source. I say 'anecdotal' as there is only verbal testimony of its existence and that restricted to less than a handful of witnesses.
Also, its method of translation is obscure, to say the least, and cannot be verified by any means.
I cannot see how there could be any comparison of 'authority' (as the OP puts it) between these two sources of information, that is to say the Greek Text of the books of the New Testament as attributed to eight authors (nine if one does not attribute Hebrews) in comparison to the English presentation of the Book of Mormon.
Purely on the consideration of the matter regarded solely on the basis of the science of textual criticism, the comparison of the Book of Mormon to the Holy Bible is, in my view, impossible, as there is insufficient evidence of the existence of the original of the former to form any substantial view of the validity of its English presentation.
The Book of Mormon can only be assessed on another basis than that of Textual Criticism. But that is the fundamental basis of the Greek Text from which we get the English Bible.
If the two documents are produced on totally incompatible methods of compilation I do not understand how their 'authority' can be 'compared'.