I don't think it will hurt the romance. Basically, all good characters (Keldorn, Aerie, Minsc, Nalia, Mazzy, Valygar, Imoen, Anomen after knighting) become cheerful when rep exceeds 18, all neutral characters (Anomen before knighting, Jaheira, Jan, Cernd, Yoshimo, Haer'Dalis) become apprehensive when rep goes over 18, and all evil characters (Edwin, Viconia, Korgan) get angry, and may leave.
The opposite is true for very low reps. Edwin, Viconia, and Korgan love that, but don't expect the good guys to hang around long for that. The Neutrals are only happy with average reps.
Cheers,
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