This was an internal tool. How will a regression in that be "highly embarrassing ... to the company"?

Wait, how was this literal incident not highly embarrassing to the company? "Our internal security team has been known to put up unapproved messages in popups that only apply to specific partners/vendors". Doesn't even matter what the content was in that context.

When you do consider the content/context, then we need to consider that this vendor/partner (IRI) was likely offended by the implications and the relationship between Google and the vendor/partner was likely damaged.

IRI did the right thing in not publicly commenting on the issue, though, so we'll never know for sure what actual affect this incident had on that relationship.

The argument was "At my job (and most jobs, I would think), if you check in any superfluous code, you’re going to be seen as a bad coder. Regressions are real and are highly embarrassing to both the company and you."

That is a bad argument in this case, because a regression in an internal tool is not going to be "highly embarrassing to both the company and you."

This was not a "regression" in any sense.

I welcome any other argument on this topic. But the argument presented had a flaw that I was pointing out.

You mean a change that passed code review and for which she was given an ok by her manager?

Tool becomes external because a customer needed the functionality. Regression was silent until the customer found it. “Whoops, we couldn’t possibly have seen that coming”.

It happens.

If you turn internal tools into external tools without thoroughly reviewing them, that's a far bigger problem.