Ha, I love the reference to "Jennifer Government" - Max Barry is one of my favorite authors.
The other possibility here is less that IBM is upset he used a "personal email" as he used a Gmail, seeing as they specifically say that first before citing the ban on personal emails. Knowing Google's practices and the high stakes of corporate espionage, they may be more wary of that than anything else. That said, the tone is pretty venomous. Someone at IBM needs to switch to decaf.
It also depends on the context of the e-mail's usage here. Has he always used his personal email for this since before he got hired at IBM (especially if IBM hired him precisely because of his prior work)? Then it gets more confusing. But if he was hired to work at IBM to work on the kernel, used his work e-mail, but then absent-mindedly used a personal email for a commit, then it's more understandable why they're upset.
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