I agree that the lps can sound very different from the cds!
I don't know Claude, I certainly, on my system, wouldn't call the difference in polarity positions "subtle." As I understand it, one way the speaker is moving in one direction, the other way the other direction, and this does not make a subtle difference to me. I agree that it doesn't make a "bad" recording "good"---but it does make a more than subtle difference in overall tonal balance, center fill, and soundstaging, to me, in my main system.
Maybe it's because my amplifier has so few parts within? I almost always notice clear differences between brands and types of tubes, interconnects, wire, footers, AC conditioning, etc.
The difference is less apparent on my other system (B&O receiver based) but after a lot of listening to my main system a lot in both polarity signatures I've learned to tell the difference better in that system as well.
It's not a big deal perhaps, but when the correct polarity (in my estimation for most JRVGs it is inverted) is applied the recordings sounds more "natural". . . whatever that means. Stereo impressions are so subjective it's hardly worth talking about them . . . .