Indeed, my problem is completely different than automatic insertion of
extenders. Indeed, I want Lilypond that it adds some "padding" automatically
to the notehead whenever there is long syllable under it, so that the
"physical" extent of the printed letters of that syllable does not overlap
with neighboring notes. If it overlaps, then it might wrongly suggest to the
singer, that the syllable belongs to a different notehead than it is ment to
belong.
The left-aligned lyrics is not a solution (it is only a "dirty" solution)
since what I am aiming at is vowel-centered alignment in all cases (
http://www.nabble.com/Lyrics---align-first-vowel-of-a-syllable-under-the-notehead-td21600612.html
as I suggest in another thread ). So, I still think it is a bug. If there is
no disagreement, I will put this into bug announcements forum. But I will
wait for a couple of days because someone can still come correcting my view.