Now, see, I always thought that the journal writer could be one of three things -
1) A general personage that isn't actually present as one of your units throughout the game.
2) A bodiless entity who follows the legion around and talks to them in their sleep.
3) A stinky gnome.
All my theories, although probably bad, are based on the fact that (a) he isn't one of the units you control and (b) it involves too much thinking for my liking =)
At any rate, we can definitely say that the journal writers in both TFL and SB are sentient beings of some type or another. That's really all I'm willing to commit to, anyway.
-Doom ?^.