The accounts are linked to the people so I don't think who is posting is in question. They are talking to each other and using their names and if they are using the accounts and posting as themselves and then using the private messaging features to communicate to others, I think it's safe to say that the accounts can be verified and proven.Trust. Blind trust.
I also think the fact someone in the conversations and part of the group has shared them means that the people he was communicating with can be verified by accessing his account (which is sounds like that is what MS was given permission to do).