Even though it might be a deliberate choice I think this is a bug:

When I was browsing the archive of the vote chess game after Team Bangladesh beat The Best ( http://www.chess.com/votechess/game.html?id=13247947 )
I was looking at how their team communicated, and noticed their discussion from when they resigned wasn't available.

I know it is not lost because I found the chat after manually completing this link http://www.chess.com/votechess/game.html?id=13247947&mv=
but i think it should be more easy to view then like this ;-)

So my suggestion:
Make resign appear as a move on the notation form.

Sometimes I am interested in reading their (my opponents) discussions when they resign too.  :)  I agree with your suggestion.