That was killed automatically because it was a duplicate comment. But at the same time Matt noticed he'd posted duplicate comments and deleted the other one.

That was killed automatically because it was a duplicate comment. But at the same time Matt noticed he'd posted duplicate comments and deleted the other one. This happens occasionally. This is one of the reasons we ask in the site guidelines that if you have a question about moderation, you email us instead of posting on the site about it. Much if not most of the time these dramatic theories about why stuff got killed are mistaken, and the actual explanation is something mundane like this.