Vanilla is a product of Lussumo:
Documentation and Support.
I can't shake the idea that Luke's in league with Mark. He certainly hasn't been given any reason not to be, that's damn sure.
I've got a really sly feeling that there's more going to between Luke and Arkady than meets the eye. Could it be possible that they have a history, pre-Kadys overdose, back when they had the most in common and were both genuinely interested in exploring 'the package'? I wouldn't be even remotely shocked to find out they were a couple once upon a time - it explains the antagonistic relationship between the two and why Kady remembers to keep an eye on him, when she's feeling particularly lucid.