The homepage is controlled from the wiki here; it includes the template Lesswrong:FeaturedArticles that google tells me is here. From the history, the editor of three years tenure has wiki username Costanza and is probably the same as the LW user of the same name.

This is just a guesstimate, not an informed answer. The Featured Articles of the week seem topical to what's happening that week, such at recent events, a national date, or new developments in some organization. I'm guessing it's an administrator who pays attention to such things closely, so maybe lukeprog. That's just the availability heuristic at work, though. It could be an administrator who doesn't post very often, but still follows events closely.