Very interesting article. It seems to me that some of the best villains emerge when even the antagonist himself isn't sure if he is a villain! And if the antagonist isn't sure ... I am reminded of a quote from a Mystery Woman mystery where Philby says something like, "Sometimes good people do bad things for the right reasons." Often villainy depends upon which side of the issue you stand. In times of war, information gatherers are called "Intelligence Operatives" by one side and "spies" by the other. Villainy may sometimes be simply a matter of perspective; from the view of the protagonist. So, to "hide" the villain in plain sight, in this context, would mean to hide the antagonist from the protagonist and thereby from the reader. Very interesting indeed.
This also raises the question, can a character be both? Villainy may not be all encompassing. A character may be heroic or noble in one arena of life (plot point) and a scoundrel in another. People are complex and complex characters can make for very interesting reading. Sometimes characters are like Jessica Rabbit. They're not really bad, they're just drawn that way!