Information: The parts of messages that will increase your knowledge over the game state if you choose to think about them.
Disinformation: The parts of messages that will decrease your knowledge over the game state if you choose to think about them.
CHAPTER 1: Reading between the lines
Like I said, I am convinced people are incapable of seeing what is information and what is disinformation. They therefore take in disinformation as information, thus significantly decreasing their knowledge on the game state and decreasing their control on the game. Clever diplomats will always hide their disinformation as information, much like advertising companies would. You feel like you are being informed, but your knowledge about reality is actually vastly decreased in the process, making your mind very much focused on irrelevancies or flat-out lies that you base your next decisions on.
Let's look at a simplified opening message:
Hi there,
It's been a while since I played this game, looking so much forward to starting over again, learning the board and all the moves xD
Anyway, I feel the two of us should not fight at the start of the game. I will move north, away from your border, you go south?
Seems like an idea that would make us both very happy

Now, I will mark information between () and disinformation between []
(Hi there,)
(It's been a while since I played this game, looking so much forward to starting over again, learning the board and all the moves xD
Anyway, I feel the two of us should not fight at the start of the game.) [I will move north, away from your border, you go south?]
(Seems like an idea that would make us both very happy

Now, you might think a player saying he hasn't played in a while is relevant information. In reality, it absolutely isn't, because even inexperienced players or bad players can make good moves if somebody else writes them or if they somehow get lucky. It gives no information.
General statements like: ''we should keep peace'' are also disinformation, because they give no information about actual moves, these words purely make an emotional connection with you, as you feel somebody on this board will be trustworthy.
The only part that is actual information in this message is him saying his moves and, more importantly, him asking you for moves to match his.
The message actually would look like this:
Hi,
I suck at this game, I don't want to fight. I will move north, I want you to move south. I like you.
Now, you might say: somebody talking about moves could be lies, therefore it is disinformation.
I would disagree. Lies would be misinformation, but lies about moves would still increase your knowledge over the game state.
Disinformation decreases your knowledge on the game state. In my opinion, anything that is said about moves being made is by definition information.
We are playing a board game, the only actual information is what moves are you making, lie or truth, that is information.
Saying you like somebody, you suck at the game, you are insecure, etc. etc. is all disinformation, because it is not connected to what is actually happening on the board in the next phase.
CHAPTER 2: dealing with (emotional) disinformation
A good diplomat will give you disinformation and gain information of his own. Since you feel you are being informed, you will share actual moves with the other player just on his general statements about not attacking you. This in itself isn't necessarily a bad thing. Giving information to your enemy can also influence them to move away from you completely, since they know you are not a threat.
However, where it gets interesting is good diplomats will make you share information that regards you stabbing them, still trading that with disinformation.
For example, they might write a very emotional message when you move in a different way than you told him:
(Hi my friend,)
(I noticed you did not move the way you said you would, which makes me a little bit worried. I feel we had a great alliance going on here and I would really like to continue this way.) [Can we agree you move your two armies back west again?]
Only the last couple of words say anything about your moves, all the rest is just banter. It doesn't mean anything, or at least; it shouldn't mean anything to you. I would always say keep your eyes on the board. The only information you are gaining is that he wants you to move your armies back, he isn't telling you anything that helps you whatsoever. The words that say he like the alliance are absolute disinformation, because they aim at influencing your decision on feelings that move outside of the board.
Keep in mind: a clever diplomat does not like you, he does not think it is fun to play with you. In the context of the game emotions are mostly irrelevant to the harshest of players. They use emotional connections to help guide your moves in a way that suits him, but when it is time for them to stab you, they will do so without any hesitation, because that is the only way to win this board game: you take centers. You don't win this game by just liking somebody.
CHAPTER 3: Inception
Once clever diplomats have established an emotional bond with you, which, mind you, is one-sided, since they are not emotionally connected to you as you are to them, they will make you move in a way that they want to. You might think your moves are your idea, when in reality, your moves will always come from them.
Every once in a while, you should step back from the board and look at the moves you are about to make. What does it gain you, what does it gain your ally?
You'll find you are not questioning yourself nearly enough, because of the previously established emotional connection the other player managed to forge with you. But emotion is disinformation in diplomacy. The only thing that should realistically influence your moves are the other players' moves, not whether they tell you they love you.
Too often people get stuck in a situation, because they are moving in one way all game long. This one way they have been moving is mostly influenced by the person who established an emotional connected with them first or best.
Be very aware of why your moves are making you happy. It is usually because the other player makes you feel smart in the game, which is a good feeling to have. Keep in mind, in every alliance one person is smarter than the other. And if you either can't or won't identify who is the smarter player of the two, that makes you the dumb one.
All this said though, this is written from my philosophy that the best of players use emotions in a way that absolutely should not work if people would look at the board every once in a while, in stead of just acting with their emotions.
Much love,
Lukan