FAANG manager here, with experience in other industries. I have definitely seen that promo committees here value maintenance work less than other industries. I think the problem is that the committee is made up of individuals from other functions, so they really have very little idea about the services a candidate supports, they're just looking at the accomplishments written in the packet. In other industries, that's typically but the case - if you run a service that has a reputation for being unreliable, you're not even getting considered.

You still have to do the above and beyond work elsewhere, but in FAANG some people will get into the conversation by ditching maintenance and focusing solely on the stretch work, and they tend to have success getting promoted.

> he could find an email that said that a customer was going to leave unless they fixed the bug

Yes, otherwise it can totally be that his impact is not that large actually.

Could be could not be, hence the hard to measure part.

I've stopped using many tools because they created just too many issues. And in that case you will not write these emails as a customer, you just leave (as long as there are better options).