I was just pointing out something real that happened. Always nice to get one or two of those. In my case, the capacitor fixed a problem. When the wire to the capacitor fatigued and broke the problem came back, so it's been verified twice. No capacitor on the coil negative, no tachometer function. Someday I might move the capacitor to another spot just to see how important location is. I can't explain it but it's a real thing. But I can't explain how my tachometer works either, or how injector pulse durations are controlled.
If you search "Kettering ignition" you can read all about how capacitors made their way in to points-style ignition systems, and the multiple benefits they have there. Seems like they started out for contact durability, then either the second benefit was a bonus or some electrical wizard did some complex math. Or both, who knows. There are some fascinating writeups out there.. That Kettering guy was pretty smart.
The electronic ignition cars still came with capacitors on the alternators, so it's not just a points thing. Maybe they're insurance against a failing sparky alternator, maybe alternators inherently generate RF interference. I don't know, but the capacitors are there.