I was reading links in the su_herald when I came across this, a debate about whether Angel and Darla had sex in the episode Angel. My first instinct was to side with those who said no, because if Angel had slept with Darla souled, both of them would have known in Reprise that sleeping with her would not cause him to lose his soul.
Then I realized something: Per AtS season 2, Angel went back to Darla after he initially gained his soul, and stayed with her for awhile. It seems hard to believe that they never had sex during that period.
I still don't think they had sex in Angel the episode - but why did they assume in Reprise that sleeping together would lose Angel his soul?