I know that seems like a random comment, but it's honestly what I feel. It's actually a "Nolanism" I picked up years back. Here's Nolan on Heath Ledger in Brokeback Mountain:
I think it's basically just a fancy way of saying subtlety. To me that's director-speak being basically that "vanity"= an actor trying extra hard to get "their stuff in" with a more broad, showy performance. There is of course, a level of vanity that goes hand in hand with all actors. These are people who play in front of a camera for a living, after all. Of course the great ones make you forget that. It occurred to me that it's probably the exact word I was looking for in regards to how I've been struck some of the bits I've seen of Affleck. Shauner made the fair point of saying it could just be the cumulative effect of the promotion using lots of these types of shots. It's definitely possible, and I hope he's right.
I wish I could get behind what you're saying, but I feel that bringing up Nolan's thoughts on Heath's Brokeback Mountain performance doesn't help your case, nor does it make for anything close to an apples-to-apples comparison. Brokeback Mountain is a realistic drama that depicted the raw, complex and sexual relationship between two men. This is a superhero film that depicts the conflict between a human vigilante and a super-powered alien being.
Due to the extreme difference in subject matter and size/scope, along with the nature of these films, any lead performance is destined to be more broad and showy than other smaller, more emotional and realistic films. For instance, Christian Bale undoubtedly and naturally delivered more showy and broad performances in the TDKT both as Bruce and Batman than he has in other films like Out of the Furnace.
And to be fair, the exact same thing could be said of you and anyone that has already made up their mind about how undeniably awesome Ben is going to be. We're all bringing baggage into this, positive or negative. It's very, very subjective. I tend to think of myself as more on the fence than negative though. I've been making sure to note any positive thoughts I have too.
To be truly fair, I wouldn't qualify myself as someone who has completely made my mind up about this film or Affleck's performance...because I haven't seen the film or enough footage to make the claim of him being incredible. However, nothing that I've seen from him or the film has turned me off it it, and if anything, I've been impressed so far. I admit that I am genuinely excited for the film and looking forward to it, unlike some. I'm also able to give credit where credit is due.
I'm not one to jump down the throats of anyone voicing a negative opinion, and there are plenty of times that I choose to stay mum -- usually when I feel people are making reasonable criticisms or conclusions and I can see where they're coming from (or when someone's clearly trolling). For instance, criticisms of Snyder's past films like MOS, too much CGI, too gloomy, etc. But when I see comments that I feel are a little silly, off-base, unreasonable, or even clearly biased, I sometimes choose to jump in and offer my two cents or call them out.
I did it for years while defending some of the ridiculous and often illogical criticisms/nitpicks of TDKR, and I now find myself defending split second glimpses of Affleck's face against claims of "over-acting" or "trying too hard", lol.
Oh, and as for that shot of Finn...yup, he's overracting. He's been over the top in a lot of the shots we've seen. However, I kind of like that way, because to me cheesy acting is one of the hallmarks of Star Wars (yes the Original Trilogy too). I'm actually worried that JJ is going to make the acting
too good, since he's such an actor's director.

t:
And here's somewhere else where our opinions differ, because when context is considered, I would not consider that shot of Finn to be over-acting at all. The dude just crash-landed his ship on a desert planet and yanked off his hot helmet. How would you react in that scenario? What should he look like that wouldn't be considered over-acting?
I can ask the same questions of Affleck's expression in the nightmare footage. It's criticisms like these that make me feel like the term "over-acting" is being thrown out too loosely and inappropriately, especially now when we're talking about mini-glimpses of actors faces in out-of-context trailer shots. It's like the new "overrated".