Music Notation/Interpretation question

[Alberto Simões]

Hi

This is not exactly a Lilypond doubt...

but imagine a chord, in a left hand piano piece, with <c d g a>

Lilypond will eventually put c and g at the left of the note stem, and d 
and a at the right (what it does exactly is not relevant for the question).

The question is:
 is the side of the note relevant when analyzing a music?

Basically, during my music formation, nobody ever told me anything about 
that. But last week, when asking a friend daughter to verify a 
transcription, she said that the notes at the right of the stem should 
be the ones relevant for the chord, and that the side of them is relevant...

Do any of you ever heard anything about that? Or did you read anything?
If so, can you share your knowledge on that?

Thank you
alberto