User blog comment:Xilinoc/Ch. 577 - SWORD/@comment-11446176-20140416080500/@comment-957629-20140416144335

Well Yumichika's two appearances have two separate release commands!! When its in the initial half-baked state he can use the second command to release the second state directly from the partial release state!!


 * Partially released blades, Shikai and Bankai are not new and can be called upon will of some users as easily as calling a fully released Shikai!! Regardless of a personality trait, this has been shown as possible!!
 * Zaraki confirms himself that he cannot seal his blade due to his vast Reiatsu, this is an established fact and until he says "I was wrong" or someone says "he was wrong" then we can't speculate that he was wrong since we know partially released Shikais exist already elsewhere!! Granted it had a nickname but it was still partially released due to something unique about that particular Zanpakuto!!
 * We know that unlocking powers and growth within your Zanpakuto requires a growing relationship with your Spirit and thus powers, abilities and appearances can change accordingly!!

I think its safe to say that a persons Zanpakuto is unique to them, we have seen different types throughout the series!! Like Kyoraku was unable to fight at his full capacity, while in shikai, until his spirit decided to fight so he was limited to blades with no special abilities!! I agree that Zaraki is a unique case, I like to think every character is unique and the relationship with their Blades are unique while still following the "true name" or "name" formula!! It could be that Kenpachi Reiatsu is do vast that without being able to seal his Blade, which was powerful to begin with, he never desired to or really required the ability to talk to his Blade!! we have seen the life or death situation being used before to open up dialogue in Ichigo's training with Urahara in that he put him in the situation where normal Pluses would either become a mindless being Hollow or find his Shinigami powers within him!! Granted it was a special case since there was already some Hollow inside Ichigo o he didn't blow apart and reform as a Hollow as usual but the life or death options still apply since Urahara would have undoubtedly killed him had he reformed as a Hollow and he also attacking Ichigo with the intent to kill after that!! Not to mention when Ichigo faced off against Zaraki, the situation promoted further growth!! Zaraki hadn't been placed in that situation before, but Unohana forced that situation upon him until it triggered that step!! Considering the strength of his blade already he never needed to ask its name, he wondered sometimes, but his blade was sufficient to win battles until this arc!!