There was a post containing images that were only going to offend people. That post was probably deleted by a moderator, and what usually happens is an explanation posted. However, sometimes a thread gets locked, and then another moderator comes along and "cleans up" the thread, including the explanation. Or mix all that behaviour up together and you get an extremely confused situation :-)
Xoops, the software that provides 99% of this site's features has a small flaw in it (this version does anyway). If a moderator wants to delete a post, a warning page prompts the user asking if they're sure they want to delete it, and that the deletion will also kill any replies to the post in question. However, it doesn't say what, if any, replies will be deleted. Sometimes double-checking (to avoid the mistake) doesn't happen.