I have Lync Online (Office 365) When we send out Lync Meeting requests, Internal Users join as themselves (normal) External Lync Users join as themselves (normal), BUT Guest users (those without Lync) always join as an internal user.
So, if internal user is John Doe. The meeting guests are ALL joining as John Doe. Even if John Doe is NOT in the meeting and has NOTHING to do with the meeting.
No matter who organizes the meeting, Guest Users always appear as John Doe in the meetings.
This occurs no matter what internal user creates the meeting request (so all the Join Lync Meeting URL's are unique)