Technically, I know that the word is formulae not formulas. That is probably changing. Language, like many human elements, evolves and changes over time. What was once absolutely right becomes recommended and then remembered and then archaic. The way to use language most effectively is to be aware of context and change. The way to use language most effectively is to develop a good ear.
That's true of most of the formulas that people use to take shortcuts in communication. Whether you read body language by the book or categorize people according to personality tests, you risk replacing accurate perception with a shortcut that will only be right some of the time.
We have evolved to understand one another and learn from one another in very precise ways. Multiple systems within our neurology work effortlessly and simultaneously to give us entry into another person's experience of the world. Multiple systems exist only so that we can communicate effectively with the people around us. When we are acutely aware of another person's experience, we can not only read their expressions and get in sync with their rhythms: we can accurately finish their sentences.
There is only one way for a normally developed brain to misunderstand people face-to-face: that occurs when a person decides to replace deliberate, honest and intense perception with preconception.
Formulas breed preconceptions (an interesting paradox).