The ability to observe without evaluating
"The ability to observe without evaluating is the highest form of intelligence."
- J. Krishnamurti
It is extremely difficult to receive the feedback, criticism, and opinions or others without evaluating what they've said and determining whether they're right or wrong, good or bad. And in return, it is extremely difficult to communicate to others without feeling judged.
The ability to do the former enables the ability to communicate without the latter.