That email you accidentally received really bothers me. I don't understand why a CS rep would get this invested to the point of wanting to cause you real harm. They're not the airline. The psychology is fascinating. There are people out there who feel like a mild short-term inconvenience to them where they have no stakes somehow justifies life-changing harm is kinda frightening, honestly.
I'm reminded of the Yahoo search data fiasco that was allegedly anonymized. Turns out, it wasn't so anonymous [1]. For one thing, people tend ed to search their home address. Whoops.
You mention writing style. We already have LLMs quite capable of copying a writing style. It's a natural extension to say we can fingerprint writing style too.
But here's another aspect. Imagine you're in a relationship with someone and you somehow fingerprint their personal data with a company. For example, you use their Netflix to like 5 very obscure movies, to the point where it's likely unique. Now imagine that Netflix's data gets released in an "anonymized" form and you can now find it based on those obscure likes. I can imagine many scenarios like this. And there's no text involved here at all.
[1]: https://www.vice.com/en/article/yahoos-gigantic-anonymized-u...