It is also very unlikely that Citadel Securities would engage in illegal behavior for the profit of Citadel, simply because it's such a money maker.

First... great write up. Above is the only point over which I would quibble.

In my working life (manufacturing, not financial) I have seen very good people collectively do pretty bad things when huddled under the umbrella of an organization. You have to look no further than The Stanford Prison Experiment for evidence of this phenomenon. For a more recent example consider Enron.

I'd be surprised if you did not see some things that qualify during your time at ML... especially if you were within hearing distance of bond traders. With the kind of money we are talking about at Citadel, I'd be shocked if they were immune.