Acetone will eat or soften many plastics.
The solvent that I use that seems to be less aggressive on plastics is lighter fluid - the stuff that people used to use in Zippo lighters.
I’d be especially careful with acetone around some of the high-gloss finishes used on some guns - eg, the high-gloss finish on Browning rifles and shotguns is softened by acetone.
Not discounting your experience ... I don't own any such ... but FWIW, 20 years of Ed's Red use has had no discernible effect on the glossy finished wood furniture on my Browning Hi-Power.
IIRC, "Zippo Fuel" is naptha, very similar to gasoline.
You're absolutely right about penetrating oils, BTW. WD-40 is nasty stuff, not a lubricant and not an effective penetrant. 3-in-1, Kroil, et al. are penetrating oils; the difference is obvious when used.