Isaiah 6:11–12 (King James Bible) and he answered until the cities be wasted without inhabitant and the houses without man and the land be utterly desolate, [a comma] and the LORD have removed men far away and there be a great forsaking in the midst of the land
The 1830 compositor set the wrong punctuation after the word desolate. His semicolon creates a full stop and thus ends up stranding the first subordinate clause in verse 12. The until-clause that starts in verse 11 extends into verse 12, which explains why the King James Bible has a comma after desolate as well as why all the verbs in the until-clause are in the subjunctive (“the cities be wasted … the land be utterly desolate … the Lord have removed men … and there be a great forsaking”). The Book of Mormon text separates off the second clause in verse 12 by replacing and with for and inserting the modal verb shall (“for there shall be a great forsaking in the midst of the land”), thus making the second clause indicative. But the first clause in verse 12 retains its subjunctive form (“and the Lord have removed men far away”), which means that there should only be a comma between verses 11 and 12 in the standard printed edition of the Book of Mormon. Given the semicolon, we expect something like “the Lord has removed men far away”. Of course, one could actually make this change of have to has (or the biblical hath) and thereby retain the semicolon. This change would separate the entire verse 12 from the until-clause in verse 11. The critical text, of course, will leave the text itself unchanged—and with the understanding that there is only a half stop between verses 11 and 12.
Summary: In the published text of the Book of Mormon, the 1830 typesetter’s semicolon after the word desolate should be replaced by the comma of the King James Bible; the initial clause of verse 12 is part of the until-clause that begins in verse 11 and requires the subjunctive verb form have in the clause “and the Lord have removed men far away”.