Update · 11:42pm Jul 10th, 2017
Okay, so apparently the feature box is either busted or got a major rework at some point, because updated fics previously featured are supposed to show up in the bottom three slots, and Discord Day Care has been there before, but for some reason it's not showing up at the moment. So hey, next-to-last chapter is up!
Getting into the updates part of the feature box isn't automatic, although previously-featured stories are likely to get there.
It works on the same heat-ranking system as the main feature box, so the bottom 3 will always be the 3 hottest updates. Sometimes you can time it and make sure you post your update when there isn't anything bigger in there ... but the time in there can be very short if a more popular story updates right after yours.
4598000
Drat. It used to just be automatic.
Ah well.