I have just stumbled over a video on youtube that contains 42 minutes of romance related party banters between our companions. After 2 playthrough I literally never heard any of this in the game. What is more, I think the only party banter I heard was really just in Act 1, and some with Jaheira and Minsc in Act 3. Any banter between my party members otherwise after Act 1 were only repeated banters that I already heard back in Act 1.
It is fair to assume this is bug, no?