User blog comment:Vazelos3/Coby as a Captain/@comment-4904935-20130611204433/@comment-1595565-20130611205502

The fleet admiral doesn't oversee every promotion given, that would be micromanaging. For all we know, Akainu doesn't even know that Coby's a captain. His dynamic with the personnel could be "Are you a read admiral? No? Then talk to the hand." Someone could go"

Officer: Hey fleet admiral, Coby just got promoted to captain.

Akainu: Here's a den den mushi, phone someone who cares.

Also, I douby he has the ability to be that picky about who gets what job. If he could be that picky, Issho wouldn't be an admiral because he has that one thing Sakazuki frowns upon, what's it called...oh yeah, compassion for other living beings. If Akainu ran things that closely, I doubt he'd let a geriatric softy like Issho be admiral. And that is how Coby made captain without being roasted alive.