User blog comment:Lia Schiffer/397: Edge of The Silence/@comment-452405-20100325225731

Okay I've read OneManga's translation and it doesn't differ all that much, so my only new thought is yes we want to know how Ichigo is special but Isshin cuts him off. In the OneManga translation his words are "You've said too much, Aizen."

So my guess is theres some sort of big secret Isshin doesn't want Ichigo knowing, or his appearence is supposed to be the answer to what Aizen was going to say as we all know Ichigo's situation is unique being a living Human/Shinigami/Hollow hybrid and remember, Ichigo didn't know Isshin was a shinigami himself so for Aizen to say it to him would've been another shock, even if we the readers already knew it.

But I could be completely wrong too, only way to find out is to keep reading and see where it goes.