As @Chris D has written, announcements are a team effort. The staff reviews, recommends changes, checks for typo's, etc., then when they are happy with the announcement, it is posted.
Has anyone thought that maybe XenForo is an artificial user that uses it's sophisticated A.I. algorithms to determine when an announcement is ready to be posted, and then does so? Disclaimer: I'm not confirming or denying that the user XenForo is an entity with A.I. that makes such decisions, read into it as you will,