I've always thought that the issues in Season 1 with smart walkers had more to do with figuring out how they wanted them portrayed - Romero has given us zombies that definitely have some vestigial intelligence, or at least memories of their former lives (I'm just considering the first two movies here). In Dawn of the Dead, after the helicopter pilot dies, he "leads" a zombie horde through the fake wall they built to protect their hideout. So, at least it had a function in the plot, not to mention being able to lampoon society through caricature.
Moving hands to mouth to eat is an animal instinct. I think you should see walkers in TWD as primitive animals. They can sit on their knees while eating like humans can (like the one that was eating a dear just near the Atlanta camp and the walker Daryl shoots before he spots zombified Merle).
The little girl zombie who picked up the teddy bear, Morgan's wife turning the doorknob, the rock walker, the walker that seemed to try to follow Rick and Glenn up the ladder and those walkers climbed up the fence were all in season 1 directed by Frank Darabont. I think he had a different view of walkers having some vestigal intelligence and memories than Mazara and others had. The RV walker was in episode 1 of season 2, which was also directed by Darabont partially. The walker that pushed away Rick's gun multiple times in "18 Miles Out", I think it was meant to be accidentally but the actor playing that walker didn't do it very convincingly. Just imagine if you are instructed to push away a gun but make it appear accidentally, I doubt all walkers seen in TWD are portrayed by highly skilled actors due to budget reasons.
Oh, and the little girl zombie with a doll? When I saw Penny 2.0 with her doll, I wondered for a moment if she becomes the zombie Rick shoots in the pilot. Probably not, but it was a nice parallel.