In the KB article https://help.sansar.com/hc/en-us/articles/115003259746-Identifying-and-interacting-with-avatars it states: "The Nearby tab of the People app identifies other avatars in the scene by Avatar Name and Avatar ID, and provides controls to Message (privately)..."
My experience with being at meetings with many people is that I am unable to send a private message to someone unless I have already offer or been offered 'Friend' status and I or they have accepted that offer.
Please state this requirement for private messaging clearly in the documentation.