User blog comment:Jallu/2 Things!!/@comment-7658432-20130416100911

First, I have 2 points. One is that they didn't know that Isshin helped them too many times. The other one is that they knew but they don't care. That's the biggest loophole of all. It wasn't confirmed nor denied if they saw/identified Isshin Kurosaki battling against Aizen. If by chance, all of them were knocked out cold, would they accept that Urahara, Yoruichi and Ichigo are the ones who fought Aizen when they were incapacitated? One more thing, after Ichigo came out from the Dangai, I'm pretty sure Rangiku saw Ichigo carrying Isshin. Isshin is her captain some time ago so I was surprised that she didn't mentioned anything about Isshin even after the events. I could say the same to Unohana who was the captain of the 4th division during Isshin's time. When Isshin and Aizen fought at Karakura, she's the only person not injured at that time. Is she THAT busy to not notice Isshin? Oh, I really think they just don't seem to care about the relics of the past. Visoreds also know Isshin for they are members of Gotei 13 during his time.

During the Fullbringer Arc, Urahara is the only one who asked. Gotei 13 for their help in restoring Ichigo's Shinigami Powers. Isshin didn't come with him in Soul Society but he's with Urahara when they delivered the sword to Ichigo. Also, why wouldn't Toshiro recognize him? He hasn't changed that much. Even his hairstyle is nearly the same as his hairstyle during his time as a captain.

TL:DR. Seems like Gotei 13 is passive about Isshin's current existence.