I'll start off with a little GEDCOM background information before firing off my questions.
The GEDCOM 5.5.1 specification distinguishes record structures (which have xref-ids) from substructures which are contained in records.
For notes, there is a NOTE_RECORD and a NOTE_STRUCTURE. The NOTE_STRUCTURE substructure is embedded by many other records and substructures. The NOTE_STRUCTURE is essentially a wrapper to either an embedded note or a reference to a NOTE_RECORD via its xref-id.
My questions are from the perspective of a GEDCOM writer:
When should a note be embedded and when should it be a stand-alone record? Are there any applications that have an explicit interface to generate NOTE_RECORDs?
I am trying to simplify my GEDCOM writer while not limiting its future expansion. I can visualize an application that offers the user an opportunity to enter free-form notes (as NOTE_RECORDs) that could later be referenced in other contexts. A NOTE_RECORD also offers the opportunity to enter a source citation, user reference, and change date.
It seems to be more common that notes are entered in the context of some other record type, and in that case it is easier to implement them as embedded.