Nikolai wrote:

ecko: Do you think that any and all in-game diplomatic actions are permissible? For instance, if I were playing in a non-team tournament that permits two players to advance from one game bracket to the next, is it okay for me to privately message another player and offer him/her a partnership through the entire tournament? I, personally, don't think that such an offer/arrangement is ethical and I see that sort of arrangement as indistinguishable from the one offered made to me in the game I started this off with.  

But that wasn't the case, was it? First of all in your case we weren't talking about an pre-game alliance or one that lasts during several games. This is clearly forbidden by the site rules. What you're mentioning now is a totally different situation, and very rare I might add (I've never played a tournament game where 2 players advance to the next bracket). And of course in this type of situation, I wouldn't be in favor of such an alliance. And think twice because it is very distinguishable from the first case imo.

Nikolai wrote:

As for disclosing non-public interactions, I think there's a distinction between breaking a confidence or trying to embarrass someone, and disclosing wrong-doing.

So which of these were you doing? All of these are lame. I think it's pretentious to play the super-hero trying to "show all the truth about the guy with the bad intentions". Especially when it's not established that what he's doing is wrong.

Nikolai wrote:

 As a result of his suiciding me, one of the players is almost certainly going to win, while the other is almost certainly going to lose. Had he not suicided me, the latter player would still have been in a competitive game.

That's his problem. Nothing ethically wrong from him.