You've got to get obsessed and stay obsessed

Not to quibble, but based on what Snape says, Death Eaters *are* Marked so JKR saying Draco is actually a Death Eater would mean he was Marked. Granted the ~system could have changed from when Snape was Marked, as when he says that he hadn't actually gone back to Voldemort yet. But apparently Regulus was Marked at 16 so there is also precedent for Draco to be Marked at that age, being from a pureblood family--which Draco is half-Black as well.