That link says,

Articles are selected for promotion on the basis of substantive new content, clear argument, good writing, popularity, and importance. Promoted articles appear on the Less Wrong home page. Non-promoted articles are still available in the other views, such as New or Popular.

But it doesn't say who does the selection. I thought it was only Eliezer. Can anyone else promote an article? Can anyone un-promote an article? Is there a vote? A sum of up-down votes from editors? What?