In Jack's first pre-wedding flashback, he does not sport his distinctive shoulder tattoo - something which is explained later in the series. Indeed, in the Blu-ray presentation, it can be clearly seen that Matthew Fox's real tattoo has been painted over.
The title is a portion of the Hippocratic Oath doctors take vowing to, first and foremost, do no harm.
Jin's handcuff has mysteriously disappeared in this episode.