I just signed up for playdiplomacy and got a game going with some of my students. Well done with the interface, message system, and I especially like what is shown in the orders history. It really gives a great view of what happened and why the results were what they were.
My suggestion is to allow the teacher to be able to see who has finalized their moves. There's been a few times now that 6 players will get their moves in, and one slacks. I understand this is probably a typical thing to run into, but if I'm organizing this with students, and I'm simply the moderator, than I think I should be able to see who has finalized what. This way, if some student is slacking, I could send them an email or a Facebook message reminding them. Like a "just waiting on you" type of thing. Also, with this ability to communicate, I could quickly figure out if someone needs a substitute and then deal with that.
*who knows, maybe there IS a way to see this, and I just don't know it since I'm new, but if not, that's what my suggestion is.
Well done on the site!!