Or was that allons-y simply the Doctor getting slight control back, like with being able to hook his foot on the chair?

I'm wavering between this, and the idea that when the entity stole his voice, it also stole his way of speaking ('the emptiness', 'the midnight sky', and so on). I'm guessing the Doctor was right in thinking that it would eventually become him (in a manner of speaking), and some of his odd... verbal quirks slipped through. Or the entity was just mocking and taunting him.

I don't know. *scratches head*