Isaiah 9:6 (King James Bible, with accidentals supplied) and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace.
Traditionally, the biblical text in English has had a comma between wonderful and counselor, thus treating both words as separate titles. The Hebrew text here is complicated. Modern English translations (such as the Revised Standard Version and the New International Version) have favored interpreting “wonderful counselor” as a single title. The earliest translations into English of Isaiah (the Coverdale Bible of 1535 and the Matthew Bible of 1537) also rendered this as a single (but different) title: “the wondrous giver of counsel”. This translation was superseded by “wonderful, counselor” (that is, two separate titles) in the Geneva Bible of 1560 and in the 1611 King James Bible.
Interestingly, the LDS editions from 1879 through 1911 omitted the comma between wonderful and counselor. The King James punctuation was restored to the LDS text in the 1920 edition. Although either punctuation (with or without the comma) will work, the standard Book of Mormon text should probably continue to follow the traditional King James punctuation (that is, with the comma). The critical text will assume that a phrasal break occurs between the two words, as in the King James Bible.
Summary: In accord with the King James Bible, maintain the comma between wonderful and counselor in 2 Nephi 19:6.