descent with modification

[Torsten]

Since Currier A doesn't contain source words with [ed], path (2) requires that path (1) must have happened at some earlier point to produce an appropriate source word.  So the process apparently needs to start, either directly or indirectly, with path (1).  And for path (1) to furnish an increasing proportion of source words for path (2), the scribe would need to be changing words without [ed] to words with [ed] more often than the other way around, perhaps not according to any strict algorithm, but nevertheless consistently over the long term.

In my eyes it necessary to distinguish between source words the scribe selects and the methods the scribe uses to modify these words. If I understand you correctly, your focus is on the source words. However, from my perspective, the key change lies in how the scribe modified these words. In Currier A, it's already possible to find words like [chdy], [chey], [cheody], or [keody]. However, at that stage, the scribe did not modify such words into words containing [ed], such as [chedy], [shedy], or [okedy]. At some point, though, the scribe began incorporating [ed] into words, making it possible to transform [cheody] into [chedy], or [shey] into [shedy]. This has two effects. First, it impacts the text, as more and more word types containing [ed] begin to appear. Second, it also influences the scribe, as such words become increasingly familiar to him.

"Now, reordering the sections with respect to the frequency of token <chedy> replaces the seemingly irregular mixture of two separate languages by the gradual evolution of a single system from 'state A' to 'state B'. Since words typical for Currier A also exist in Currier B, but not the other way round, it is reasonable to assume that the order shown in Table 2 indeed represents the original sequence in which the sections of the VMS had been created."

If path (1) were to be followed consistently, the proportion of previously-modified source words containing [ed] would steadily increase, and path (2) would then also be more likely to occur because the probability of selecting a source word that already contains [ed] would go up, leading to a kind of "snowballing" effect.  This is the (subjective, human-powered) mechanism I assumed you were describing here, but maybe I read more into your explanation than you intended. Did you have a different mechanism in mind for the gradual evolution from Currier A to Currier B?

If you would remove the word "steadily" I would agree with your description. In my eyes it is more an up and down since the text is changing from page to page. See for instance the pages in Currier B. The folios f107r/f107v did contain less [ed] words than the folios f108r/f108v (You are not allowed to view links. Register or Login to view.). This even happens for folios of the same bifolio (see the number of instance for [ed] on f111r vs f111v).

One open question is why the "snowballing" effect occurred with words containing [ed], but not with words containing [eod], despite the existence of words like [cheody] and [keody] in Currier A. I have some ideas, but I don’t have a definitive answer to this question. One idea might be that for some reason in the eyes of the scribe [o] was not interchangeable with [a] before [d] and therefore in some way "dispensable" (You are not allowed to view links. Register or Login to view. only list 47 words with [ad]).
Note: After the Curve-Line-Hypothesis a line glyph like [a] cannot precede a curve glyph like [d]. Possible glyphs after [a] are line glyphs like [i], [r] and also [l] (see You are not allowed to view links. Register or Login to view. or "Die Harmonie der Glyphenfolgen" by You are not allowed to view links. Register or Login to view.).