Impropriety varies by culture. What's proper in one society may be improper in another. Wearing shorts to a business meeting may be seen as an impropriety in some cultures.
Pro Tip 2/3
Perception of Wrong
'Impropriety' often implies a public perception of something being unsuitable, rather than a personal opinion. The director faced criticism for the perceived impropriety of his decisions.
Pro Tip 3/3
Subtle Incorrectness
The word is used for slight misalignments with expected behavior or norms, not always for severe wrongdoing. There was a sense of impropriety in his informal dress at the formal event.