Personally, the best conversation I've had in the game I've had... on guild chat. Cop out? Maybe. In that case, I'll say some of the best conversations I've had about the game have been in the general Molten Core channel. In there, I've chatted with others about guild progression, bragged about our downings, and even gotten confirmations on a few boss bugs and glitches. Most people in there seem pretty helpful and adult (not surprising, probably, considering everyone in there might actually be an adult).
So where have you found good chat in the game-- or isn't there any to find at all?