While preparing a course, I came across Stendahl’s complaint (in 1963) that the Nestle editions treat Rom 7:25b as belonging to Rom 8. Which made me wonder how that looks on the page, and whether all Nestle editions do so. Stendahl of course used NA25 (1963) or an earlier edition, not NA26 (1979) or later.
It turns out the subdivision was introduced in the 10th Nestle edition (1914), as the bottom of p. 405 may show:
For comparison the same portion in the 9th edition (1912):
Interestingly, NA26 and NA27 (1993) have a major division between 7:25 and 8:1, but still set 7:25b apart as a subparagraph.
In doing so, these two editions draw even more attention to the conjecture according to which 7:25b is an interpolation. This conjecture was first mentioned in the 16th edition (1936), and attributed to the Dutch pastor Michelsen (1879), but there happens to be an earlier author, namely Peter Aloys Gratz in 1814. It has found support among a good deal of Pauline scholars.
In NA28 (2012), the conjecture is no longer mentioned, and there is no subdivision any more between 7:25a and 7:25b. The only trace still left of these typographical wanderings is the capital letter of the first word of 25b, Ἄρα.
See Krister Stendahl, “The Apostle Paul and the Introspective Conscience of the West,” HTR 56 (1963): pp. 199–215, p. 213 n. 30 (= “The Apostle Paul and the Introspective Conscience of the West,” in Paul among Jews and Gentiles and Other Essays [Minneapolis, MN: Fortress, 1976], pp. 78–96, p. 94 n. 20).