Personally, I don't have any interest in Diplomacy. However, if the bulk of the online multiplayer crowd buys it and plays it exclusively then I'll have little choice but to purchase it if I want to keep playing online.
I am hoping that online players can get together and agree NOT to get it for two reasons. (1) From what I can tell, it's not going to do much to appreciably improve the online game and might worsen the game. (2) It will just further subdivide the online multiplayer community. I don't see how it's going to be good for us.
I respect your efforts to improve the online community, I really do; but this kind of contradicts the whole 'lets make the online community more friendly' thing. Diplomacy adds options to the game, even to locked team games, and will presumablely curb the game-ruining 'feed' strategy. If nothing else it will make the pirates an interesting part of the game again, seeing as everyone just turns them off these days because they're useless fodder. And the online community wants to boycott over this?! No offence, but it sounds like you just don't like change. It you had some genuine concerns over the expansion, or it cost $30 or something I could understand; but all this is doing is overhauling the much neglected diplomacy aspect of the game and pirates. And it costs $10. For anyone who still plays Sins even a few times a month this is pretty much a no-brainer purchase. If the ICO community does not want to change, that's their choice. But don't expect anyone to take your 'why not try online?' posts seriously anymore.