Function(s) of condenser in points-type ignition system?

In modern transistor ignition systems, where the transistor replaces the points, a capacitor on coil (-) is not used. A modern IGBT transistor has only a few hundred pF of capacitance, a value much less than a points capacitor. The use of a large capacitor, charged by prior ignition event, would result in a transient current as transistor turns on. The IGBT transistors have built in voltage limit, collector to emitter, that clamps over voltage, for protection. The limit varies by specs, but typically 360 to 500V.
The capacitor on the coil (+) is desirable, it provides an AC path, with lower impedance, than the lengthy wired path back to battery. Improved spark, and reduction in RF emmisions.