But even without that amazing talent that is essential for a live action actor
to survive, an animator can gain insight and find nuggets of ideas to use within
their shot from looking at live action reference of themselves (or better yet-
others) acting out a sequence. I think Carlos' "editing" paradigm is a great description. I don't think I've ever had a shot where I used only the live action reference as a creative input. It's always a combination of thumbnails, pulling ideas from your sketchbook, flipping through your notebook of interesting things you've observed in your daily life, discussions with the director/supervisor or other animators, live reference and acting it out to get a feel for how a body would be within itself for such a moment. (another tip: take up some kind of activity that forces you to control your body for results. This will begin to make you self aware about how your body moves in space and interacts with itself.) All of these bits are creative possibilities, the results of your scavenger hunt for ideas. Then you sit down and sift through the pile to find the best bits and assemble your shot from there, taking great care to plan things so that they combine to make the shot work as a whole and not feel like an M-TV edit of scattershot ideas glued together.
Getting to the core of the question: My final shot never matches the exact timing or mechanics of whatever live action reference I do use for that action. But what the final version of the shot does have is the essence of that action, captured and condensed, boiled down to it's core idea. Even if it's a subtle thing, it ends up being refined in the animation process to be an even purer expression of the moment.
-k