The phrase 'damn all' is informal and best suited for casual conversations or expressive writing.

Informality

'Damn all' stresses someone's complete lack of knowledge or understanding in a blunt manner.

Emphasizing Ignorance

Using 'damn all' can convey frustration or annoyance about the negligible amount someone knows or cares.

Stresses that very little has been done or achieved, often to underline someone's laziness or neglect.

Often used to criticize or express disappointment in someone's lack of contribution or effort.

'Damn all' implies that even minimal communication or action has not taken place.