Why: austerity performed with deluded understanding, through self-torture, or for the purpose of harming another, is declared to be of ignorance, naming the darkest version of this practice, one aimed at harm rather than growth.

In life: any form of self-discipline that's actually oriented toward harming yourself or someone else, rather than genuine growth, has fundamentally crossed into something different and worth recognizing as such, regardless of how disciplined or committed the effort looks from outside.

Teaching: if you notice a disciplined effort of your own has quietly become oriented toward harming yourself or someone else rather than genuine growth, name that shift directly, this verse treats it as a fundamentally different category, not merely an intense version of legitimate discipline.