The original text of the Book of Mormon sometimes allowed the subject to be repeated as a pronoun when there was an intervening participial clause, as here in Mosiah 8:7. Similar examples of repetition for which the sentence-initial subject is followed by being can be found in the current text:
The original text in Mosiah 8:7, with its repeated subject I, is clearly possible and will be restored in the critical text.
There are, of course, other possibilities. For instance, when the participial clause is not too long, the subject is frequently not repeated, as in these two nearby examples:
On the other hand, there can be a connective wherefore or therefore before the repeated subject, as in these two nearby examples:
Thus variation is possible—and one of the possibilities is to pronominally repeat the subject without any connective wherefore or therefore.
Summary: Restore the repeated subject I in Mosiah 8:7; pronominal repetition of the subject without any connective sometimes occurs after an intervening participial clause.