[He stares at Felix a moment but his gaze is a little absent and the Doctor's brow creases into a frown, mulling over what Felix said because that's just it; the Doctor doesn't hide, not physically, at least.]

No one should have to hide or cloak their identity at all. [Yet he has been doing it for centuries.] Thank you. I'm sorry to hear that you understand that so well. I think... I wonder that perhaps the Mara might have helped that along.

[Another subject broached, the reason he wanted to speak with Felix in the first place.]