When the dead stay silent (and other gripes about dialogue)

A little too closed-mouthed, Michonne???
I’ve become a total fangirl of The Walking Dead, but even total fans can have the occasional gripe and, yeah, I got one.
Minor spoiler alert for what follows! So beware if you read on!
For a show wherein the characters take a lot of time talking about their feelings instead of, oh, fortifying their perimeter and making a plan for where to meet if a herd comes through and they get separated (Season Two, I’m looking at you), those same characters are quite adept at not relaying legitimate information for no reason I can see other than that the screenwriters don’t want it revealed at a particular moment.
Rick’s big secret from the CDC doctor I sorta get. But Carl not mentioning the swamp zombie? They’ve set him up to be impulsive, but not stupid.
I can even forgive that, but Rick not telling Lori exactly what happened with Shane? (And then Lori getting all bent out of shape about the whole Shane thing even though she’s the one who sat Rick down and said that Shane was dangerous? Um, hello?). For folks who spend a lot of time chatting, they managed to talk around the important stuff rather than about it.
But the one that really got me was in Season 3, this last episode. There’s Michonne, who’s witnessed Merle taking Glenn and Maggie. She’s heard that Merle is looking for his brother. She can see that Merle knows Glenn. She knows that he has lost a hand.
So what does she do when she gets to the prison? She entirely and completely fails to mention that Glenn and Maggie were taken by a one-handed man who actually knew Glenn and who was looking for his brother. Why? Because the screenwriters willed it to be so. (And no, I don’t buy that it’s because she’s so close-mouthed naturally; she did tell some information–such as what they said about how to reach the prison–and relaying the rest only strengthens her position that she should be treated as an ally, not a prisoner.)
That’s the kind of thing that pulls me out of movies and books, because it’s so contrary to the way the characters would actually behave. “Just say something!” my husband and I will scream at the TV. “Why the hell doesn’t she (or he) just say X?”
I get that it’s hard as heck sometimes to move the story forward in the way you want it to go if you have to reveal certain things that another character knows. (You also see this in books where you’re in the murderer’s point of view, but he/she never things anything damning. Uh, really?) It’s worth working on those scenes, though, to make the characters feel more real and the scenario more believable.
Here’s the thing, Walking Dead writers: I love the show. I love the characters. But let the characters do the talking and keep the writerly manipulation invisible. Please, please, pretty please!
What about you? Did those scenes bug you, too? Did you notice or just go with the flow? Do you get irritated when you see the writer’s fingers in a book or movie or tv show?