In my admittedly limited experience with DA i am finding that many times the OP would not have to ask the question if they knew how to ask it. The answer would be self evident. (Learning Drupal is like learning to walk on water: you have to find out where the stepping stones are.) Consequently, comments evolve into discussions in an attempt to better define or debug the issue.
Moving discussions to chat is a desirable alternative, but there is no simple method to initiate a room between two users unless the number of comments triggers an automated invitation, and, more important, I have no way of knowing that a response has been made in chat unless I maintain an active window on the room.
For what it's worth, I think that chat would be better used if we had a simple method to initiate an invitation, and if we had the option of having responses sent to our inbox.
There seems to be a general misconception about this issue. It is not about privileges, or uncontrolled private messaging.
Prefix the whole issue with "If the privileges are in place ..." and we can eliminate that chestnut.
Currently, if the number of comments reaches a pre-set limit, a message appears to encourage the users to move the discussion to chat. Selecting the option, a room is created for the OP and the Answerer. I would like to see this available much sooner so discussions could be moved out of comments.
Because SE users span the globe, if might not be convenient for the chat to be real time due to differences in time zone. I would also like to see inbox notifications for replies.
I agree that social networking is not a desirable feature for Stack Exchange, and should be resisted. However discussions of issues help to drill down to a root cause, eliminate misunderstandings, and aid in the search for a solution which is what Stack Exchange is about.