It's a fascinating subject alright. I did a little googling, hoping to find a straightforward description of real-world diodes and the kinds of capacitive and/or resistive snubbers that might be employed in parallel or series with them. What I found was mostly confusing, contradictory, and/or irrelevant. I have not found a good simple model with which to explore the details.
Certainly slamming on and off the current through the transformer windings will produce rapid changes in the magnetic forces, which will produce mechanical force on the iron parts. It seems reasonable that an impedance element - capacitor , resistor, and/or inductor - could slow the transitions. If the impedance is small enough to not have much effect on the performance, then its effect on transient energy is probably confined to radio frequencies, or at the lowest the transformer resonant ringing which is typically in the 50kHz-100kHz range. But of course that's just speculation on my part.
For what it's worth, the intrinsic capacitance of a UF4007 diode (as used in the Paramour) is on the order of 10pF, so I would not expect an additional 10pF to make a substantial difference. Snubbers are usually more like 10nF (0.010uF) I think.
Here's an off-the-wall point: In some cases, the power line voltage is asymmetrical and may either have DC riding on it, or a DC current can be generated in the power supply because one diode does more of the work than the other. Any DC current through the transformer can lead to a substantial increase in vibration. Various schemes have been proposed to resolve this problem if it exists, but - again - Google leads to a confusing mass of unsubstantiated speculation along with a number of interesting things to try.