User blog comment:DaNASCAT/Technical Update: July 9, 2013/@comment-5691231-20130709210734

I've actually found it necessary to have the summaries for closing threads. Most of the time when I close a thread it just looks like I've closed it for no real reason. But because of this update, I should be able to add a reason to why I closed it so users will understand.

So yeah, the summaries on closing threads is a nice update :)