You have dialogue choices, but having him talking definitely imposes restriction on how you can interpret the character.
I don't really see how that's a problem. I would rather the game have a fleshed out character with dialogue than a dull blank slate only open to my interpretation. This isn't an RPG where you create your own chracter, this is a story driven game where the protagonist has a relationship with the world around him and many of the characters in it.
It really takes me out of the experience when the entire world is reacting to Corvo, but he just stands there motionless and speechless. It works in Half Life and Bioshock, but not in a game like Dishonored where there is so much interaction with NPCs.
and that interview is pretty hilarious, because that's exactly how I felt about Dishonored.
I hate what Valve does with the silent protagonist. I find it incredibly awkward and really creepy
though I do agree with him when you apply this criticism to Half-Life 2 and it's episodes, there is too much NPC interaction there to believe that Gordon would not say anything.