I've noticed that, mixing origins you can get more than one time the same special ability: as a general and "official" rule, do these bonuses stack? For instance, if I create a Human Mage Wizard Charismatic I would get the Encouragement Special Ability twice: would I give +2 morale buonus (stacking the two bonuses), or just +1 (not stacking them)?

I think they should stack, even if they are "named" bonuses, because it would make sense trying to specialize the character giving them coherent adn recurring "personality traits and attitudes", rather than saying "Oh, I would like to choose this talent, but I already have this bonus from another source, so I'm going to choose something else. Yes, this is metagame thinking, but many players of mine share this approach.
This is just an example, but there are other possible examples, so I would really like receiving an "official" answer I've not been able to find in the core rulebook so far.
Many Thanks,
Fenn