I think we need to see some mathematical equations to really figure this out. I do NOT claim to be able to do these equations, but I think someone should try and quantify the claims that are being made.

It just seems odd to me that so many people are able to strip their lockring threads if skidding doesn't exert any additional force on your bike. It also seems odd that skidding hurts your knees more than regular cycling. I, for example, had been riding my road bike for a long time before I got a fixed gear, and I notice a lot of unusual soreness in my knees from riding fixed (presumably from practicing my skids).