[K2543] Function of capacitor C1

My Mercedes w108 runs much smoother since it got upgraded with the K2543. However, I have a question about function of capacitor C1. My understanding is that it will conserve the energy of the back-EMF from the coil (=good), while also forming a LC tank circuit (=bad, since it influences your next spark).

Is this correct? If so, would it not be better to use a freewheel diode instead to protect T2 by dissipating the back-EMF?

Thanks in advance for any clarification!

This classic kit was designed more than 30 years ago. The people that designed it are no longer with this company, so I’m afraid we cannot ask for their advice.
Since then, the kit has been on the market, unchanged. It is one of our best selling kits, so the circuit has proven to be reliable as-is, without modifications. We dit not develop any similar circuits, since the ignition systems on modern cars no longer need this upgrade, so unfortunately at this time, we have no experience with this matter.