Semantically equivalent scores look different

[Erik Sandberg]

Hi,

I have a bunch of works I did before 1.4.12, when the polyphonic music had to 
be done manually, without <x \\ y>. Recently I have ported a few works that 
used the old syntax, to use the modern < \\ > syntax instead. Though the 
music should be exactly equivalent, it happens that the spacing is different 
between the versions (and it happens that the difference is significant, e.g. 
one version can occupy more space than the other).

The difference between the notes can be something like this (though it only 
happens in more complex examples):
Old notes:
\context Staff <{\context Voice = A a \stemUp b \stemBoth d \stemUp e 
\stemBoth g} {\context Voice = B \stemDown s c s f s}>
New notes :
\context Staff {a <b \\ c> d <e \\ f> g}

Is this a behaviour you might consider a bug? (lilypond solves an 
optimization problem, and if pieces that should be considered equivalent end 
up in different solutions, then something might be bad). If you are 
interested, I could try to find a Real Example, but I won't if you don't 
need it (unnecessary work is not good).

Erik