Editorial Variants and Reader's Notes
Ulrich Schmid wrote that "rarely, if ever, do we consider editorial activity, even complex editorial decisions, as the source of variants." [in "Scribes and Variants Sociology and Typology" in H. A. G. Houghton and D. C. Parker (eds.), Textual Variation: Theological and Social Tendencies? Papers from the Fifth Birmingham Colloquium on the Textual Criticism of the New Testament (New Jersey: Gorgias Press, 2008), 1-23]. Schmid recognises that editorial activity began long before scribes commenced the copying process. Editorial variants came to fruition during the stage existing copies of texts were acquired, compared and edited for publication. This suggests that editorial variants were well thought out and planned and that scribes were merely copyists of these well thought out and planned editions. Whoever was responsible for the production and reproduction of an edition, whether a well-to-do individual or guild, was also responsible for some of the important and significant variant readings we find in the extant manuscripts of the New Testament. An example of such editorial variant that Schmid discusses is Romans 16:25-27.
Schmid also discusses the existence of reader's notes on the margins of MSS which were not due to scribal hand. Luke 17:14 of P75 is cited as an example here. Schmid believes that Matthew 27:49 may also have its origin as a reader's note.
Other than the writings found in Houghton and Parker's Textual Variation: Theological and Social Tendencies? are there any other works which address editorial variants and reader's notes?