A publication by Virginia Commonwealth University provides 7 Steps for Providing Constructive Online Discussion Feedback Successfully.  Their suggested template for feedback includes:
  1. Start with something positive – “You did very well in this week’s discussion.”
  2. State the grade and reason right away – “This week you earned 20/25 points.”
  3. State the correction as a reminder or recommendation – “Remember, five postings are needed for full participation points.”
  4. Provide an example or tip to reach the goal – “Here’s an example of a solution that earned full points.”
  5. State your expectation – “In the upcoming weeks, I will be looking for….”
  6. Remind them of available help – “Your success is important to me, so please email me when you have questions.”
  7. End with something motivational – “This was a tough assignment, but you did well overall.”
The complete article can be found here.