Yes, there is little penalty to not role-playing alignment.
Some minor spoilers
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However, I think it makes the game more interesting. When I played an evil character, I took the chance to demand money before any job I did. I took 128 gold from Nalia and didn't clear out her castle. When I visited the Druids, I took the evil alternative offer (won't spoil that one). Yeah, I caught heck for it when I returned to Trademeet, but hey, I was evil.
BG2 has so many playability options, I like to save some for particular scenarios. I take the evil path and pick up Viconia and Korgan when I play an evil PC. I take the good path and pick up Anomen and Keldorn when I play a good PC. In my opinion, it makes the game even more fun to see what the next dialogue sequence will bring.
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Most Subtle Official Straightman of the Laughing Hyenas -- Grammarian Brigade.