Why is middle C (C3) given the absolute pitch designation
c'?
Would it not make more sense to use just plain old
c
as middle C?
Middle C is usually called C4 if numerical octave indicators are used (the Acoustical Society of America
System) It can be called C3 if named by a MIDI octave designator. Anyhow, the correct name for middle C in the alternate Helmholz system used by Lilypond is indeed C'. C without any indicators is one octave below, in the small octave.
So, in short, no, it would not make more sense.
What would it take to alter this in the code, if I wanted to do so for
my own version?