I think there are times when a supervisor should take part in informal communication, but knowing when to engage with staff in this manner is vital for the credibility and authority of the supervisor.
For example, most supervisors should maintain a personal distance between themselves and the people they manage.
Engaging in informal conversation breaches this ethos, which is why it is not recommended.
However, in moments where team bonding or empathy are required, then it can be advantageous for the supervisor to show a more "human side" by engaging in informal communication, in order to earn trust and additional respect from staff members.
However, it is important they refrain from making the informal communication a frequent habit, otherwise they will struggle to maintain a sense of authority.
