I'm 100% certain if I were writing code to print boarding passes I could have done better.
I appreciate the scale of the system. If your argument is that such a large system cannot be more bug-free than it is, we can just agree to disagree.
But if you're saying it's not worth it financially to fix these bugs, then we can at least agree with that.
Introducing bug fixes may ship additional bugs. That's a real risk.
The scale of the system needed to get you and your luggage flying overseas in an economically viable way says a lot about how amazing the current system is. But sure, complain about HTML tags being printed and assume you could do better.