The jacks used by Sony are the same for line-out and headphone.
I think the Kimber connector is from Switchcraft. When I was testing minicables, I had a RS patchcord that hung up on the lineout, and got rid of it fast; that one also felt rough to my fingers, and I think the Sony jack is catching on the edge of these plugs, where the metal rings and the plastic insulators between sections come together (in fact, I can see this on the RS adapter - there are tiny nicks in the metal). The Canare F-12 work fine, but there is less of a noticeable difference between the heights of the insulator and metal sections.
ADDED LATER THAT EVENING: I picked up two more RS adapters tonight on the way home, one gold and one nickel, and peeked inside the Sony with a minilight. The Sony jack has two cylindrical spring-like pieces of metal set at right angles to the jack, and these contact the plug on the curve of the cylinder. Each has two circular cutouts on the side, parallel to where the plug does, so they're sharp. The RS adapters -- gold-plated or not -- do indeed have undersized insulator sleeves (the plastic rings between the three metal parts of the plug). So they're uneven and have sharp edges (every other plug I looked at, even from RS, is far, far smoother, with insulation and metal matching much closer).
The combination of jack & plug is definitely dangerous, because the edges on both come into contact and lock. The jack would lose the fight, in the long run.
I'd say the problem is RS's, not Sony's, but they could share some blame, and maybe Switchcraft as well. The plugs ought not to be finished that way, because it will abrade any jack's contact points, and could even break them.