I agree with error3. The game is cooperative AND competitive. In fact, competitive questing is one of the main features of the game, if I recall correctly.
"Competitive questing" just means that players could occasionally have conflicting goals.
They are still supposed to be cooperate most of the times, not to actively fight each other on sight.
Also, in a party-base game where everyone is probably going to have a specialized role (and equipment), it's even hard to imagine how stealing each other's loot should make much sense.
Know what? I will be EXTREMELY curious to understand how they are planning to balance challenges ahead in a way that works for players who are cooperating nicely and for those who are going to "split the team in two and go their own way".
Look, if they can come up with a reasonable "solution" for this even better, but you should probably keep expectations in check about this competitive questing thing...
And maybe try to make the person you are playing with just more reasonable.
