Agree and even better would be that type of information under the story header so anyone who was following the thread knows that it has been closed and the reason as well.
ADP Begins to Roll Out a Zenefits Competitor; Thread Closed [n]
Where "n" is simply a number that is listed elsewhere that describes the reason for closing. Note that can scale to any number of reasons or explanations either existing or new as if it's a footnote.