Why do people refer to Missling as Dr.? Because this is a scientific endeavor and in academic and scientific environments obtaining a PhD is considered a significant achievement and worthy of recognition. On most of the conferences I have heard Missling introduced as Dr. Missling.
It is standard protocol.
On the board the TGD reference came as a response to a number of posters denigrating Missling and his educational background. It has stuck. It's also quicker to type than Missling.