The Rebbe always made those who entered his office feel comfortable.
I remember once an envoy from the King of Morocco came for a private audience with the Rebbe. He arrived a few hours early and respectfully asked me what the procedure was for an audience with the Rebbe. I told him that there is no procedure, and that when he enters the Rebbe's room he will know what to do.
In general, the Rebbe's chassidim would not sit during a private audience or shake the Rebbe's hand. However, this was never policy, and most people who had a private audience would sit down. In fact, the Rebbe would regularly invite those who entered to sit and would shake the hands of the men.
It seems that by the time the envoy entered the audience with the Rebbe, he had asked some of the rabbinical students what was customary behavior and what was not. They had told him that the custom is not to sit or shake the Rebbe's hand.
When the Rebbe extended his hand to him, the envoy said that he was told that the custom is not to shake the Rebbe's hand.
The Rebbe responded, "Don't worry, I will not tell them that I shook your hand."
