In the OLD (pre-Spohr) days, there was no chinrest to my recollection.
My students and their parents say that the violin "sounds louder" and "feels better" without a chinrest.
When I have the violin in an erect position, I can touch my left hand to my right shoulder even without a chinrest and with a protective cloth. This is the posture that Aaron Rosand taught me - though he thinks I'm crazy for having ditched my chinrest.
In this posture, I use my left hand to raise the scroll so that the strings are parallel to the floor. However, I do not hold the violin "flat" - I keep it at an angle consistent with my clavicle.
When I go into higher positions, I don't have to contort my spine to play really high positions. I can stand there with a straight up and down spine and just play. I've gotten a lot better at this since last year when I first ditched the rest. Now I stand pretty much without head tilt.
I also feel more natural with bowing and vibrato nowadays. When I vibrate, I vibrate in the plane of my neck and not in a vertical fashion.
My assistant has a long neck, and she's taller than me. She has to have a chinrest.
As a beginner violinist 22 years ago, I didn't have any physical discomfort until my mother started warping my posture due to the physical theatrics she saw violinists doing on TV.