When ACN was first introduced, there was an issue wherein the cutscene following the first fight at the crates would be interrupted due to you getting hit by AoE from others doing the same fight. It was said at the time that they were making it so that you would be invulnerable in cutscenes to avoid this issue.

This appears to not work all the time. This weekend I did Taking the Black, the quest to unlock BLM, and was interrupted in the cutscene following the fight at Highbridge three times due to others attempting the fight while I was viewing the cutscene.