On the face of it this interests me not in the least and I don't have any real desire to find out why Capaldi's Doctor has the same face as Caecilius or the guy from Torchwood. I'll obviously give Moffat the benefit of the doubt that he can make an interesting story of it, but it's easily the most dubious I've felt about a story direction. It's just the same actor. Assuming it's more than a throwaway line, obviously.
The caretaker does say you will be revisiting old faces not just the favourites. Maybe this somehow refers to it.
Aside - been watching Capadi's 2013 role as Leonardo da Vinci from "Inside the Mind of Leonardo". Holy CRAP are we in for some awesomeness. Mark
Peter Capaldi presents quotes from Machiavelli's "The Prince" (1 minute in and throughout): [yt]http://www.youtube.com/watch?feature=player_detailpage&v=FSwHqnbHpvo#t=60[/yt]
The Silurians tried to steal the augment virus from Doctor Khan Noonien Songh, but their skin conditions started to dissolve and they lost their mouth love organs. They kidnapped Strox as the nurse most familiar with earthling scum physiology to develop a cure, but it only made them grow a second heart, glow like crucifixes and get nausea during changes in time. They tried another plan, but they only impregnated the timeline with Doctor Khan Noonien Songh's DNA and would periodically regenerate into him. Moral of the story: Playing the superhuman game is dangerous, kids. You get the most unfortunate of relatives.
Believe it or not, Paul Cornell offers an explanation for Peter Capaldi in "The Girl Who Loved Doctor Who," the comic book coming out from IDW on Tuesday. (I read it this week, as it actually shipped to comic shops this week.)