Yeah, there's still something funny going on with the shifter. I didn't really get any definitive answers from NASIOC, other than to replace the bushings (which you didn't think would present a problem on a car as new as mine).
I'd take a look at some of the possible issues that you came up with, but I don't really know what to look at. I'd also have to get some of my tools from work.
This image shows the interior and exterior end of a typical gearshift cable.
The black nylon-covered part of the cable is the "Conduit". It consists of an inner liner (Teflon, PBT, nylon, etc.) surrounded by the "Laywires", over which the black jacketing has been extruded. If it has been heat damaged, the shifting will be very "spongy" and "draggy" (especially draggy if the liner isn't made from Teflon).
The "Conduit End-fittings or "Ferrules" are crimped onto each end of the conduit. They provide an attachment feature for at the reaction bracket / cable mounting bracket at the transmission and for at the shifter front flange (Rear flange if your name is Mr. 2) It is typical for a spring-steel clip to secure these connecting points, although clipless attachments are getting to be more common. If the clip is missing, the conduit end-fitting backs away from the bracker / shifter when the cable corewire is under tension loading. This can make things feel spongy in one shifting direction and not in the other.
The conduit end-fittings may also contain bushings that help isolate noise from shifting, engine noise and transmission noise. These isolator bushings are protected inside steel cans and rarely go bad.
"Support Tubes" that swivel extend from the conduit end-fittings toward the transmission shift levers and/or shifter output levers. If they are broken or pulled out of their swivels, the corewire will be unsupported under compressive loading and will kink and fatigue where it bends. Shifting will feel real spongy at first, followed by real draggy as a sharp kink forms and then it can either seize-up or free-up as the corewire breaks in two.
The "End-Rods" are ~1/4" diameter steel rods crimped onto the corewire ends, typically with eyes/rings for bushings at the tips. These attach to pins or ball-studs on the transmission shift levers or the shifter output levers. May self-retain to the ball-stud or a groove on the pin, or require a clip or pin (and maybe a washer or two) to be retained. If an isolator bushing is used to smooth the shift and reduce NVH, it may eventually become cracked, etc. and need replacement. This would result in a spongy, imprecise shift feel.
"Environmental Boot" or a "Wiper Seal" may be used on the exterior end of the cable to keep water, dirt, noise, fumes, etc. from getting into the cable. Water will freeze in cold weather and dirt just makes things feel gritty and wear out sooner.