I use the affectation too, and I'm sorry it bothers you. However, I think some of the comments you've gotten are right on the money-- it's shorthand, and relates to a sense of control and planning.

In my latest fic, a great deal is proceeding out of my unconscious, not my conscious, mind. Therefore I feel out of control, and yelp about Qui-Gon refusing to talk to me to tell me what he's planning to do. I like saying "he" is talking to me because there are parts of me that identify with him, and understand him (both on a conscious and unconscious level), and when they pull together to produce good stuff that I haven't consciously planned, it feels like an organic and discrete process, at least slightly separated from my own regular thinking. It's something I actually enjoy, at times, when it works well. It feels rather like free-fall.

I am aware that it's all me and my conscious and subconscious concepts of him that are producing what happens in fic; I never think that there's a real blue ghostie out there whispering in my ear...

That's me, anyway, but maybe some people like to remove themselves form what happens in their fic because they don't want to own their kinks? Or perhaps they want to be separate from the quality of what they produce? Blaming the story events on an outside force might absolve a bit of responsibility...

Or I can even think how pretending the actual character is speaking would lend a fic an air of authenticity, at least in the immature mind.