I do use the phrase "characters talking" metaphorically, but as ellenfremedon said, it's shorthand for a more complicated process. I write for the most part in a series of intuitive leaps, & I don't always know where a piece is going when I begin it. When I say a character insisted on such-and-such, it's a metaphor for the total process of intuiting some new emotional stance & then mentally testing its boundaries. Will this work? Is this plausible? Could I write this, or this, instead? Verbalizing something like that is difficult, & if the author doesn't feel as though she's in control of her own writing, yes, it does feel like the characters are writing through her.

Hm. It seems to relate to the degree to which an author writes intuitively or from a plan, & the degree to which she feels connected to & in control of her own work.