Hi,
indeed is was going to make a not so polite reference to the same point.

There is considerable science indicating that rectifier/capacitor input devices produce harmonics which degrade the AC supply quality locally.
Even if you don't really care about the quality of the supply or difficulties that the line supply company it is highly probable that harmonics generated
buy one piece of equipment, a servo or VFD say, conducts that noise into other devices connected locally like PCs, and motion controllers.

And VFDs are often marketed as power factor correction devices, as they rectify, AKA draw current in phase with voltage. As opposed to an unloaded or partially loaded induction motor powered directly from mains, which has a horrible power factor.
Then why do VFDs have such a poor power factor? They may draw current in phase with the voltage but the current distortion badly and negatively affects power factor.

This is from Yaskawa:

A good way of understanding power factor is to consider the equation:
Power Factor = Cos theta/(theta[1 + THD2])
where: theta = displacement angle between fundamental voltage and current
THD = total harmonic current distortion
The above equation takes into account fundamental displacement and harmonics. Both affect true
(overall) power factor.
Craig