Coitophobia

Coitophobia (Phobia of Sex) is mentioned on GURPS Horror page 25.
This notably gives immunity to seduction attempts, similar to how Social Disease imparts Immunity to Seduction to those aware of the disease of a person trying to seduce htem.
B165 also does that with the neutered and sexless quirk which gives points unlike sterility as a 0 point feature.
B16 mentions Will is used to resist seduction attempts, so these disadvantages actually impart infinite will. Sort of like how No Eyes gives unlimited HT bonus to resist blinding (better than Protected Vision)
B126 Clueless by comparison only gives a +4 bonus to resist seduction due to being "oblivious to attempts".
B127 mentions "You are no more susceptible to Fast-Talk than normal, save when someone is trying to convince you that an attractive member of
the appropriate sex is interested in you . . ."
It doesn't mention what bonus to Fast-Talk (or penalty to resist it) would exist here, but a -4 would be reasonable since that's the penalty to Savoir Faire or to the IQ roll to realize one is the butt of jokes (though that's not actually established as being a raw IQ roll otherwise)
category:Phobias