An error occurred while saving the commentAnonymous commented
I see this as a security measure that should be chosen at the organization level. It appears you cannot add a 3rd person to a 1:1 conversation for (what I think are) insignificant reasons. Many users start a new conversation with one person and realize they need to add someone the next day but they have to start over in a new conversation.
This has been causing a lot of annoyed users. How could they know to add someone if that person wasn't know by the originating party until after the chat was started? This is a PROBLEM and needs to be opened by Microsoft per organization.