[split] Line padding, layout, Currier's "groups of letters"...

[Torsten]

Indeed, but until this day it is not clear to me what he meant, or what he saw.
The two characters that seem to fill this role are Eva-m and Eva-g, but they don't appear in little groups, and they also occur elsewhere.

There is no doubt what Currier saw since he also gives an example: "The ends of the lines contain what seem to be, in many cases, meaningless symbols: little groups of letters which don’t occur anywhere else, and just look as if they were added to fill out the line to the margin. Although this isn’t always true, it frequently happens. There is, for instance, one symbol that, while it does occur elsewhere, occurs at the end of the last 'words' of lines 85% of the time" (You are not allowed to view links. Register or Login to view.).

In his example Currier explicitly refers to 'words' ending in EVA-m (You are not allowed to view links. Register or Login to view., footnote 17). EVA-m occurs in 62% at the end of the last word of a line (see You are not allowed to view links. Register or Login to view., p. 18).

After Currier the scribe was able to select groups of letters or 'words' which fitted into the available space. With other words the lines fit into their margins because the text layout was made during writing. Currier probably calls them meaningless since someone writing meaningless dummy words can easily select words as needed for a given layout. 

D'Imperio also described a similar idea in her book 'The Voynich Manuscript: An Elegant Enigma':
A message concealed in a Longer Dummy Message "would explain the many strange repetitions of highly similar words in close succession; one of the words represents a part of the actual message, while the rest are nonsense sequences made up, like meaningless babbling, and inserted to conceal the true cipher string. The scribe, faced with the task of thinking up a large number of such dummy sequences, would naturally tend to repeat parts of neighboring strings with various small changes and additions to fill out the line until the next message-bearing word or phrase. This phrase would also explain the frequent illogicality and lack of consistent sequential structure in stretches of text which has so frustrated students" (You are not allowed to view links. Register or Login to view., p. 31). 

This way the strange 'rare characters' discussed in this thread are just further examples for the lack of consistent sequential structure.