I think my rationale, at this point, would be his voting. There really isn't much to go on. He seems to show up only right after appleguy posts, and then disapprears (I could be wrong about that). And last round he was one fo the few to not change his vote. It could be a matter of keeping low profile or just not spending a lot of time online.
I still wouldn't rule out Don't Panic or Nathan either.
17 credits can do that to you.