Isaiah 4:3 (King James Bible) and it shall come to pass that he that is left in Zion and he that remaineth in Jerusalem shall be called holy
In this passage, a sequence of four italicized words in the King James text (“that he that is”) has been altered to “them that are” in the Book of Mormon text; that is, the subordinate conjunction that is omitted and the singulars he and is are replaced with them and are. The 1920 LDS edition edited the object pronoun them to the subject form they. Such dialectal usage as “them that” is found in another biblical quote in the Book of Mormon:
This nonstandard usage appears to be intended. For related examples of nonstandard usage, see pronominal determiners in volume 3.
The passage in 2 Nephi 14:3 has a plural subject for remaineth. As already noted (in the discussion of rebelleth in the 1 Nephi preface), the original Book of Mormon text permits plural subjects for verbs ending in -(e)th. In this instance, the 1837 edition omitted this ending, thus ending up with two plural verb forms, are and remain (“them that are left in Zion and remain in Jerusalem”).
Summary: Restore in 2 Nephi 14:3 the original nonstandard language of the Book of Mormon text (“them that are left in Zion and remaineth in Jerusalem”).