Anyone use a cartridge demagnetizer?

NO!!!!  Perhaps the gentleman should look at a general review of how MC cartridges work and what they are made of.  If you were to somehow degauss the rare earth permanent magnets inside each of the coils you’d permanently destroy the ability of the cartridge to reproduce electrical signal output. It is the motion of the coils inside the magnetic field of the two permanent magnets that creates signal voltage. That’s electromagnetism physics 101. Luckily the coercivity of those rare earth permanent magnets is so high that you’d have to stick it inside the magnetic field of something like a nuclear particle accelerator to degauss them. 

what would cause a cartridge to require demagnitizing?  As far as I figure, nothing.  Any voltage going through it are AC voltages.  And the levels are so low, they probably couldn’t in any way affect magnets, or ferrous materials, and if they were strong enough, they would be demagnitizing, not magnitizing, as AC is what is used it demagnitizing devices. 

My Luxman E-250 phono stage includes an "articulator" switch on the faceplate.  It's purpose is to degauss the coils that move (moving coil) in the magnetic field created by the stationary magnets. The idea is that demagnetizing the coils will allow those coils to respond more "articulately" within the magnetic field of the stationery magnets.🎼

Lotta misinformation here. Demagnetizing definitely helps, needs to be done regularly, but especially with a cartridge (MM or MC!) needs to be done carefully. 

Anyone in doubt is encouraged to do a little reading on magnetization. Very simply, magnetization happens when a strongly oriented magnetic field is presented and then cut off. This is exactly what happens with music, where the signal is constantly swinging positive to negative. In fact this is exactly how we demagnetize! There is however one very big difference. In demagnetizing the amplitude of the signal is gradually reduced to zero. In music the amplitude is all over the place. Wires are never perfect, they all have areas small or large that can become magnetized. The result is that gradually over time playing music results in lots of isolated little magnetized regions in wire. 

Demagnetizing is simply an alternating polarity field that starts out very strong and then smoothly fades out. The strong field assures getting even highly magnetized areas, and the smooth fade takes it all back to neutral, demagnetized.

That's it. It ain't rocket science. It can be done any number of ways- sending a signal through the wire, playing a smoothly fading track, manually holding a powerful demagnetizer near and then moving it smoothly away. All of these work great. Just try them and see.

Reality check here: phono cartridges don’t use ferrous wire in their coils. No, repeat, no chance of them becoming magnetized.