User blog comment:Sicarius001/Royal Guard and Eighth Division Captain/@comment-5551986-20130423223428/@comment-8295743-20130424064721

Everyone wants Renji to be promoted, because he's a fan favorite character. He just isn't that strong, even with Bankai. He's not much of a leader, has almost no strength in terms of Kido or Hakuda, and I get the feeling he doesn't do much in the way of practical works as a Lieutenant(Neither does Shunsui, but he makes up for that in other areas). He just isn't captain material.

Not convinced that Senjumaru actually created Kido, as Kido is just manipulation of spirit energy. She might have created the "main" spells though, or a few spells of particular importance.