Terrifying because there are cases with poor interoperability, or terrifying because the metal model is non-trivial?
If you mean the former, that's certainly a pain point on the web (although it's worth noting that some of the specific issues Jake mentioned are already fixed in at least Firefox nightly). For that reason tests like these are being tested in the web-platform-tests project [1], which is part of the Test The Web Forward initiative [2] aiming to create a common, cross-browser testsuite which all vendors can run in automation so that they are able to detect this kind of issue during development and avoid compat-affecting regressions of the kind seen here. Firefox runs (almost) all the web-platform-tests in its CI system already, Chrome runs a subset and are looking to add more, Servo runs the cubset corresponding to the features it supports, and what Microsoft and Apple do is a mystery to me. I believe the Jake is going to look at submitting his testcases, and I hope that in the future web authors will see the value in investing in their platform by submitting tests and bug reports when they run into interop difficulties.
If you just mean that the lowest levels of the web-platform are quite complicated then yes, but it's not that surprising (and the things that are complicated to implement are not necessarily hard to use; document.write is a tremendous pain to understand in detail and implement, but people nevertheless use it with reckless abandon).
It's weirdly prevalent in ads apparently. Like, to the point that you get a pretty ad-free web by just shipping a browser without document.write. Actually, that doesn't sound like such a bad idea...
If you mean the former, that's certainly a pain point on the web (although it's worth noting that some of the specific issues Jake mentioned are already fixed in at least Firefox nightly). For that reason tests like these are being tested in the web-platform-tests project [1], which is part of the Test The Web Forward initiative [2] aiming to create a common, cross-browser testsuite which all vendors can run in automation so that they are able to detect this kind of issue during development and avoid compat-affecting regressions of the kind seen here. Firefox runs (almost) all the web-platform-tests in its CI system already, Chrome runs a subset and are looking to add more, Servo runs the cubset corresponding to the features it supports, and what Microsoft and Apple do is a mystery to me. I believe the Jake is going to look at submitting his testcases, and I hope that in the future web authors will see the value in investing in their platform by submitting tests and bug reports when they run into interop difficulties.
If you just mean that the lowest levels of the web-platform are quite complicated then yes, but it's not that surprising (and the things that are complicated to implement are not necessarily hard to use; document.write is a tremendous pain to understand in detail and implement, but people nevertheless use it with reckless abandon).
[1] https://github.com/w3c/web-platform-tests [2] http://testthewebforward.org/