User blog comment:Relikz/Chapter 364: Tartarus Arc, Part 1: Immorality and Sinners, Review./@comment-5036235-20131220080517/@comment-7418318-20131220103156

Well... Zero is his original personality, with the Brain-personality being the tamed down version thanks to the seal.

Re-casting the seal would certainly have made him less troublesome to deal with in prison... or maybe the seal reformed by itself once the others had recovered from their wounds and exhaustion.