Comment #5 on issue 3160 by [email protected]: chord names pushed into the staff
http://code.google.com/p/lilypond/issues/detail?id=3160
In the text interface, the "" symbol has an empty extent (so negative height), not zero-height. I agree with you that a zero-height element should stay. However, by definition, an empty skyline has nothing in it, which means that measurements cannot be taken between it and adjacent skylines.
I agree with Keith, therefore, that 3156 is the way to go for empty skylines. If, however, you want to redefine "" so as to be a point stencil instead of an empty interval, then that's a trivial change and can be proposed in a separate patch.
