I think that this spell would increase in some way good/evil RP, and will force
other characters by identifying (if they can) an evil character from his actions, obviously if you are known for being a serial killer or evil necromancer this spell would have no use for you since you are known for your reputation, but it would help greatly those subtle ones.
Undetectable Alignment
Abjuration
Level: Brd 1, Clr 2, Pal 2
Components: V, S
Casting Time: 1 standard action
Range: Close (25 ft. + 5 ft./2 levels)
Target: One creature or object
Duration: 24 hours
An undetectable alignment spell conceals the alignment of an object or a creature from all forms of divination.