That's something we've discussed at length and will probably implement someday. It's pretty challenging, though, to do it the way we want, and other stuff has to get rolled out first.
Quick and dirty would be to manually update and append "Thread Closed [n]" to the header with a message like this:
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.
