The GIL is a good example because it removed optionality from Python by having its semantics leak out. Using a poorly performing tool is a different problem en

The GIL is a good example because it removed optionality from Python by having its semantics leak out. Using a poorly performing tool is a different problem entirely. Most of the really horrible errors in SW design involve choices where the semantics above will be visible and encoded as a subtle (or not so subtle) dependency that cannot later be fixed without an infeasible level of effort. I deal with these regularly and they are the true original sin in most sizable software projects.