The 1837 edition introduced the subordinate conjunction that before the first “as many”. This change was not marked by Joseph Smith in the printer’s manuscript. And one might wonder whether it is necessary here. The 1830 and 1837 editions both had a comma after “I say unto you”, so there was no crucial need to insert the that in order to prevent misunderstanding. The 1920 LDS edition removed the comma since it was unnecessary given the following that.
When we compare this example with other examples of clauses preceded by “I say unto you” and beginning with as, we find five cases in the original text where that precedes the as:
Note, in particular, the example in Mosiah 4:11 where there is first an intervening parenthetical as-clause (“as I have said before”), which is then followed by the subordinate as-clause that complements the verb say (“as ye have come to the knowledge of the glory of God”).
But there are also two cases that are similar to the earliest text for 2 Nephi 30:2—that is, in both cases the that is omitted in the earliest text:
Note that Alma 23:6, just like Mosiah 4:11, has a parenthetical as-clause (“as the Lord liveth”), but in this case the following as-clause (the one that complements the verb say) has no that.
In the majority of cases where a choice is possible, the subordinate conjunction that occurs after “I say unto you”, but in over a third of the cases, no that occurs:
When “I say unto you” is followed by yea or nay, we never have that (40 times). Similarly, the that is omitted after “I say unto you” if the independent clause is a question (13 times), an imperative (13 times), an inverted conditional clause (3 times), an exclamation (1 time), an adverbial (1 time), or a simple noun phrase (1 time). Otherwise, we find examples of both possibilities, although examples with that dominate.
Summary: In agreement with the earliest textual sources, remove from 2 Nephi 30:2 the intrusive that; a comma after “I say unto you” helps facilitate the original reading.