Capacitor for a PWM controlled DC motor

I am currently completing the assembly of a small coil winding machine driven by a 12V/45 mA PWM-controlled motor.

At two different robotic oriented sites I have found the recommendation of adding a capacitor to its terminals allegedly to protect the motor.

If true, what is the actual reason to use it? How to calculate / check the value of C?

I don't think it is so much to protect the motor, as it is to reduce noise in the circuit (and perhaps protect the driver); usually, a small disc capacitor is used - but as far as size is concerned, I am not sure where you start, or if there is a way to calculate it...?

I did find this discussion:

https://www.wattflyer.com/forums/archive/index.php/t-2915.html

Here is a site with good input. It is really for brush noise.

https://www.electro-tech-online.com/custompdfs/2010/07/motor-noise-reduction.pdf