Board Thread:General Discussion/@comment-24815992-20140622184501/@comment-24384892-20140622211427

Her being the original Kenpachi is one of the reasons why most Shinigami, including captains, feared her. The reason why most Shinigami are aware of her past as a bloodthirsty killer is because she's one of the legendary original Gotei 13 captains, thus making her one of the oldest and strongest captain. There's no way anyone in the Seireitei would not know about that.