I suppose if that's your definition of a social game, then Lion's Arch 2 is the on the frontier of MMOs. However, map chat does not a social MMO make. I could have had the same experience playing Inklink on shockwave.com back in the day. In fact I probably had more fun doing that because the chat was half the game itself.
Youtube the game you'll see what I mean.
Try using that experiment in GW2 for every zone, you would get 1/10th of the people playing the game using ingame chat.
Ok let's forget your assumption then that PoE players just somehow have more respect for their fellow gamer than GW2. Another plausible reason for no chat flooding: a minority of those players aren't chatting. They're playing their solo game. Just like this one.
And no, to anyone who thinks so, i'm not bashing GW2. I have no doubt that this game will be very well evolved by the next official expansion, but as of right now, the game feels extremely underdeveloped moreso than it was in the BWE's.
My point is this: These forums were designed with socializing in mind. They are a place for vocal players to congregate and discuss the game they love/hate. In other words, this site was built for a very specific social layer of GW2 players.
Equating this with globe-wide chat doesn't make sense. By enlarging the scope of chat, you don't fundamentally pivot the game towards socializing. You do this by enhancing the social aspect of the game itself. Give players more of a reason to group up and experience the game. Give them a reason to care about the content and the world their avatars inhabit. Then see how socializing explodes and flourishes.