The security breach nonsense is just that, ridiculous nonsense.
You enter a password on a private computer, hence it may or may not be available to its owners. If there is a domain set up, it may or may not be in plaintext on the domain controller already. The password is not your secret, it is a shared secret. Shared secrets allow for trusted and possibly encrypted channels to be established. That's not your identity!
It's my company, I may as well set up an account with identical user names and passwords on each of my computers, which everybody knows, and who is to say its not within my right to do so? I worked in such an environment, there was no trouble whatsoever. It's not your call.
Putting someone's real name in the real name field of some domain account changes nothing, it is not nearly enough to prove anything in court. No, even if your boss have not ever logged in (which is basically improvable), that IT guy fed up with stupid stuff probably has superuser rights and could do whatever he wants and no one will ever know.
The idea that company-generated credentials automating authentication and delivery of access to company-owned infrastructure and information that the company willingly shared with you to automate some work processes in the way the company sees fit somehow entitles you to anything is blatantly, irrefutably absurd.
The company can set up whichever automation and authentication procedures it wants and yes, your boss can do whatever they wants. Unless, of course, their boss says they can't, then you go to their boss.
Surely, nothing implies whether these are some good or bad practices in some particular senses. That's for the company to decide, not you.
Surely again, if we're talking some kind of fraud, that's whole other issue. Logging into your company-provided e-mail account may be A-OK, but sending an e-mail to your wife with your signature at the end is not.
Please notice it is not necessary to log into any of "your" accounts to do so, but that still constitutes wrongdoing.
Committing the code you wrote in working hours on company's private computer, which you got paid for, to company-owned repository and build farm is A-OK (from whichever corporate account the company wants it committed from), but adding malicious backdoor code and then claiming you did it is not.
Please notice it is not necessary to log into any of "your" accounts to do so, but that still constitutes wrongdoing.
See where I'm going here?