To use computing slang to talk about music: this is just ricing. At best you'll sound out of tune with the rest of the band, at worst you'll run into wolf intervals and other issues with just intonation.

This touches on the biggest reason we stick with 12-tone equal temparament in the West: social reasons. Having a standard means we can play together, in groups or at jams, without having to negotiate which tuning system we use (an argument most working musicians I've met see as utter wank and a waste of time).

Is ricing a computer term? Thought it was a (funny|racist) reference to JDM cars and how engrossing a hobby tweaking those cars can be.

Yea, it definitely has racist undertones related to import tuners. "Rice" implying "asian." I find it a bit uncomfortable to read people posting their customized Linux desktops, for example, and calling them "riced out."

I only ever heard this as a car culture term.

Maybe I'm showing my power level a bit here. To me it means "tweaking something's aesthetics in a way that doesn't improve, perhaps even degrades, performance".