Flashbacks serve some of that purpose in the visual representations, but lots of the actual emotional and mental content is left as an exercise for the reader. And with the internal models that all people build of other people, fanfic writers build those models from what they see and create involved and intricate and quite fascinating representations that they can then send spinning in their own directions. It's a fascinating exercise.
So fascinating that I was a complete fool and just signed up to do ten fics for June for the springkink community. It's going to be quite a ride. *laughter* And I guess I just kind of decided to explode out from Bleach by working five other fandoms.
Of course, this little discourse does not explain, at all, why the heck I signed up for a Dresden Files (the books) piece, though having it be Murphy/Kincaid is really, truly the reason as I love those two tough characters immensely.