The list to the right of vacant properties is a little out dated. Some problem and vacant properties are now occupied and part of the positive neighborhood fabric. In 2007, back when the ANC Kevin Chappel had a website, one of the October posts was titled "Vacant and nuisance property on Warner". I can only gather that 420 Warner was once that vacant property.
It isn't vacant any longer. It was most recently sold a few years ago to its current owner and resident.