Continuity mistake: When Angel grabs Cordelia's hand as she apologies after telling him to "get over it", the position of Angel's hand changes between shots.
Disharmony - S2-E17
Continuity mistake: In some of the shots in the scene with the red bird, it is raining and in some shots it is not.
Other mistake: Angel implies that Wesley told him the device will kill Illyria. But this Angel is from earlier in the timeline, as shown when he tries to tell Wes and Spike things they have just told their Angel. So Wes did not tell this Angel that the Mutari generator will kill Illyria. Angel should know nothing about it. (00:36:30)
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.
Continuity mistake: When Lorne covertly warns Angel that the hotel is bugged, he places a note in Angel's pocket with his hand on Angel's shoulder. When Wolfram and Hart watch the video feed later, the hand that was on Angel's shoulder is now in front of Angel's chest. (00:22:50 - 00:37:00)
Plot hole: During the scene where Angel tries to work out where Wesley is being held hostage we learn that the man Faith beat up at the start is still alive in the hospital and that it's his apartment she's staying in. Angel bursts into the apartment to save the day, but that's not possible without an invitation, as the owner is alive, whether or not he's actually there. (00:34:00 - 00:36:40)
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.
Revealing mistake: When Wesley accidentally turns off the power, the room briefly goes dark, then lights up with moonlight/streetlight from outside. In the real world, that light would have been visible the whole time in the background. (00:01:45)
Revealing mistake: Just after Angel kills the quan-eyed demon, he exits the room behind the smashed mirror. On the widescreen DVD you see Angel's reflection in the mirror to the right of the smashed mirror (even though vampires don't have a reflection). (00:03:40)
Carpe Noctem - S3-E4
Continuity mistake: When the gang rescues Angel and returns him to his normal form towards the end of the episode, Cordelia shocks him unconscious with a taser and he falls to the floor, lying on his front. But when Fred whacks him on the head with her baseball bat, he is suddenly lying on his back.
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.
Continuity mistake: When Wesley is explaining that Angel feels like he doesn't belong in the world, the amount of donut he's holding changes. (00:13:30)
Plot hole: When Angel is being pursued by the Lilliad demons, he is holding his son Connor and is talking to him in the car. Later on it is revealed that he is in fact holding a teddy bear with a bomb attached to it. If it wasn't his son, why was he talking to it? It couldn't be to fool the Lilliad demons because they wouldn't be able to hear him, as they were in separate vehicles.
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.
Visible crew/equipment: When Angel is fighting the demon a cameraman is visible rising on the lower right. (00:27:13)
Visible crew/equipment: When Angel kneels down to the fridge a camera lens is visible in the top left. (00:15:21)
Visible crew/equipment: When Angel is drop kicked to the floor a camera LCD in the lower right is visible. (00:24:35)
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.