It would be nice if bash were not a moving target. I have run into several bash incompatibilities in real life. Bash on macOS differs substantially from bash on Linux because it's much older. But bash is also generally somewhat poorly designed, leading to lots of aggravating and puzzling behavior for "corner cases" and this behavior not infrequently changes between versions.

So for example set -u for the longest time used to trigger on defined but empty arrays (which is hardly an obscure edge case), but what workarounds are possible differs quite a bit between versions:

https://gist.github.com/dimo414/2fb052d230654cc0c25e9e41a965...