Character mistake: When the bidding for Cordelia in the auction reaches $20,000, somebody bids for $30,000 after the auctioneer has said "going once, going twice" and they end up winning. The auctioneer should have in fact restarted saying "going once, going twice" after the $30,000 bid was made.
Character mistake: When Faith arrives in LA she is carrying a bag. She puts it on the ground and then steals a man's jacket and wallet. Afterwards however, she leaves without picking up her bag.
Blind Date - S1-E21
Character mistake: Angel comments that Vanessa was acquitted because of a hung jury. A hung jury means the jury couldn't come to a unanimous decision; the case would require a new trial, while an acquittal means the jury found her not guilty, and she couldn't be tried again for the crime.
Character mistake: In this episode, Gunn wonders how he could have lived in Los Angeles all his life without knowing about all the "weird ass stuff" going on. But flashbacks in "Double Or Nothing" show that he knows demons exist there.
Heartthrob - S3-E1
Character mistake: In the first flashback to Angelus and James in Marseille, Angelus briefly speaks with his modern-day American accent before reverting to his Irish accent.
Character mistake: Near the end of the episode Angel says "All I did was beat up a tiny Texan" referring to Lindsey. But at the end of season one Lindsey told Angel he was from Oklahoma.
Smile Time - S5-E14
Character mistake: While Gunn and Lorne are interrogating Framkin he sings a couple bars of a song "Courage and Pluck". However, though he has the ability to read people when they sing, and in fact in the very next episode knows that Fred is about to fall from just the words "you make me happy", Lorne doesn't read him.
Answer: Due to his epiphany, Angel basically had the 'true darkness' he worked so hard to reattain ripped away from him, like his soul was after sleeping with Buffy.