Is tonearm bias a compromise, maybe a myth?

Tony...as a fellow left-hander, I sympathise :)

You must have nerves of steel m8! ("DJ scratching" - in the "safe" direction - on your protractor :) :)
I'm usually a quivering wreck just making routine adjustments :)

It reminds me of NSGArch's repeated appeals that platters be secured during cart alignment to avoid any accidental cantilever reversals. Sadly, few of us - including myself - take this simple precaution (I will next time, I promise!) :)
On my turntable, I've noticed that after deceleration the platter comes to rest with a final small oscillation (backwards-forwards, about 1mm or so, for a split second). Perhaps wrongly, I attribute this to the rubber belt stretching alternately either side as it grapples with the heavy platter's inertia...
It doesn't encourage the idea of not being present during a power failure while a record is spinning! :)

Tony, When the stylus is tracking an actual LP, the friction that causes skating has everything to do with the grooves.

The main friction is between the vinyl and the stylus, but yes, groove modulation adds additional drag to the stylus and therefore creates additional AS force as Lewm points out. I found some data on the internet a few months ago. Research was done on various types of vinyl and shellac records decades ago. The coefficient of friction varied from 0.2 to 0.6. That coefficent number would have a direct impact on AS force along with groove modulation. I believe that most modern vinyl records have a fairly consistent coefficient of friction- probably in the 0.2-0.25 range, but that is only a conclusion based on that research data. Friction force is your normal force, eg. 2 grams, times the coefficient of friction. So if the coefficient is 0.2 then the friction force would be 2 grams times 0.2 or 0.4 grams and the AS force will be a component of that friction force. AS force is going to be friction force times the sine of the angle between the stylus and tonearm pivot, I believe. While tonearms may have AS force calibrated in grams for the sake of simplicity, the real AS force acting on the stylus is much smaller than that. Someone correct me if I am wrong with that conclusion. But that is why you really have to dial in AS force by listening rather than just setting it and forgetting it. The tonearm makers have to use average values while stylus angles, horizontal compliance and friction forces can vary which have a direct impact on AS forces.

Tonywinsc, thanks for the explanation. It corroborates with my experiences, we must listen. The downside of using our ears is that errors in other areas such as VTA, optimum tracking weight can influence what we hear and the process for dialing in a cartridge in all set up parameters is iterative in nature. New cartridges in particular or rebuilt cartridges should be rechecked for VTA, tracking and antiskating force after running in for a few weeks/months.

Quite a few romantic and interesting views of AS, carts, and arms here, but they are quite confusing and some, just plain wrong. Virtually all carts, both MM and MC with a conventional cantilever, have a rubber suspension damper. This is for obvious reasons and to control high frequency response. The natural HF rise is controlled by damping. This trades off imaging/phase linearity for FR, but it's a necessary compromise and prevents ear bleed and excessive cantilever excursion.

Carts are not preloaded with cantilevers to the left(?). Perhaps this can be verified with a cart designer like VdH or J Carr. Cantilevers should be close to centered when at rest. If your cart came with the cantilever SLIGHTLY off-centered, you can align to the cantilever rather than the body. A linear arm exhibits no skating because there is no offset. The stylus/cantilever should be free to track in either direction. there is no pre-canting.

Yes, AS is applied to the arm near the bearing, while skating occurs at the stylus. But it's the arm mounting and its offset that causes skating. That is the relationship between the plane of the cantilever and that of the stylus to bearing. Just because groove velocity and arm position have an affect on skating, doesn't change the basic cause or solution.

AS force has the affect of reducing VTF, slightly. This could have something to do with perceived SQ degradation. I haven't experienced this. A minimal value of AS would tend to center the image and balance the channels. If you don't have a scope or appropriate software, a tape deck with a good display will show this. Just because optimal value of AS is a compromise, doesn't mean you should throw the baby out with the bath water. My 2 cents anyway.