When an announcment is published, the latest always displays at the top. There are many occasions where you might want an important announcement to remain at the top of the list until removed.

 

For example, you might want to announce an upcoming outage. When first published, that announcement will display at the top of the list. Subsequent, but less important, announcements will push it down and possibly out of sight.

 

I suggest giving the admins the ability to make the announcement "sticky" so that if flagged as such it remains at the top of the list.