Thank you Noeck.
Your explanation makes sense and I feel it might be close to explaining the issue, although in the log it appears as though the edition-engraver only sees two voices, not three, thus refering to them as
Voice.B and
Voice.C instead of A and B doesn't work either.
Most intriguing to me is that if I explicitly create the voices as you showed, so that no voices are created implicitly, like here:
\new Staff \with { \editionID LH } {
\new Voice = "Implied" {
\clef F <<
\new Voice = "LH_A" \relative c' { \clef F \voiceOne e8 d c4 d8 c b4 | c8 b a2 g4 }
\new Voice = "LH_B" \relative c { \voiceTwo f2 e | d g,4 c | }
>>
}
}
Then I can't tweak the first note of either "LH_A" or "LH_B", but I
can tweak any of the following notes.
Anyways, at least now I can use a structure that works properly, which was the intent behind my original question. Although I'm still curious as to what is the reasoning behind this behavior, it is clear that it far exceeds my (lack of) understanding of the inner workings of Lilypond. So it's unlikely I'll be able to find an explanation on my own. If someone finds it I'll be more than grateful to hear it!
I attached the full example of what I described above in case it is useful to someone.
To the openlilylib guys, since I'll be learning to use your tools, tell me if I can be of use somehow.
Thanks!
Stéfano