Drew Eckhardt 

Should right broken G-spring retainer in a pre-1998 (not the 1998 and newer design which relies on the post to support the clock-spring; this is an original 8-speed shifter which I installed a 9-speed index ring) pointy-hood shifter have any effect on shifting performance?

The G-springs seem to be correctly located with no slop and the ratchet ring bears on both halves.

Has any one else put a broken one back in there?

My shifting got soft and started occasionally slipping to a smaller cog when I stood on the pedals so I opened up the shifter for the next G-spring replacement and found that I had both a G-spring with a missing tip plus a broken retainer.

A couple hours driving to bike shops which 'had the part in stock' didn't produce a pre-1998 replacement, JB weld didn't hold after left to cure over-night, and I didn't want to be waiting a few days to ride so I put it back together with new G-springs.

I'm hoping I don't need to re-rebuild it when I get a replacement via USPS express.

FBinNY 

Generally cracked rings expand under the tension of the G springs, so it may not hold fast against the tension of the RD return spring. But if yours is one of the old metal body versions where the spring ring is held in place by 2 split pins, that might make up enough rigidity to get the job done, at least for a while.

You've nothing to lose by trying except a few minute of your time.