balloonGrobText

[Noeck]

Dear all,

I try to use the balloonGrobText. After I found out that I have to add
it to the Score, Staff _and_ to the Voice, some questions remain:

1. All spanners have zero length if a balloonGrobText is attached to
them. At least Beams, Hairpins, Slurs, PhrasingSlurs, TupletBrackets are
affected. Is that a known bug or am I doing something wrong?

\version "2.16.0"
\new Voice \with { \consists "Balloon_engraver" }
{
  \balloonGrobText #'Slur #'(-1 . -1) "Text"
  g( a)
}

2. I cannot attach a balloonGrobText to a Tie. Why?

3. Why does this Text appear two times (already before the break)?
\version "2.16.0"
\new Score
\with { \consists "Balloon_engraver" }
{
  a1
  \balloonGrobText #'BarNumber #'(1 . +1) "Text"
  \break
  a1
}

Cheers,
Joram


PS: Why such a strange name, balloonGrobText? Why not just annotation?