There is a distinction between discipline and punishment. It seems your sister-in-law doesn't know what it is.
If this thread holds true there will be not one post asking a non-beater how well their methods worked and what techniques they used.
That is because any success would be anecdotal at best, and disingenuous at worst. One might as well ask a communist about economics.
If the child doesn't require corporal punishment, there is no need for it.
And you would know that how?? I've watched the "non-corporal" punishment sister-in-law in action, and her attempted applications of discipline were exactly according to Dr. Spock--they just didn't work at all.
"If this thread holds true there will be not one post asking a non-beater how well their methods worked and what techniques they used."
Maybe because folks know from experience that such "non-beater" (a very "cute" phrase, by the way) methods, for the most part, don't work for most children.