We frequently do this to help avoid misinformation - our forum is for a mobile app, we need to be careful with users requesting support so they get the best experience with their first point of contact 
Being able to control who can reply would be beneficial for some objective categories, such as in this case. We already make extensive use of groups and PMs for handling a large percentage of our support (including email-based support), and it works a charm, it’s just the people that choose to request support publicly that may not be getting the most accurate information the first time around. Appreciate your input, Jay!