This word we're talking about is something you either know & feel or not
you are not just saying "I feel this". that would be unassailable. all personal reaction to art is valid, some of part it is obviously inarticulable.
you are saying "this is truth, and I know what what it is". I, James Brown, Cornel West, whoever, we know, but not everyone does.
you are saying e.g. that I and others who know, have a better ability to discern this truth. we are, literally, more soulful.
that - as demonstrated by the quoted YT comments and infinite other examples - is exactly what is nonsense
you can't have it both ways - personal knowledge and thus unassailable, but also a universal artistic quality equaling truth
if it "goes without saying" , then you - no one - can
say this has soul and this does not.
either it's articulable and can be defined, or it's inarticulable in which case, whereof one cannot speak, thereof one must be silent
look at your arguments - what is soul? the soulful. why is it soulful? because it's played with soul. or, because Cornel West (or whoever) says it is.
it's either soul in terms of itself (meaningless), in relation to some equally meaningless synonym, or because x authority says so
but no person has any more inherent ability to discern artistic truth than anyone else. not you, not me, not Cornel West or James Brown, no one.