This demonstrates how any algorithm, software or not, works: Start with something desirable or necessary and add complications until you end up with a mess that can be used to yield arbitrary results, drive outsiders into madness, and summon some lesser demons if read in a chanting manner.

Now what could be done about this? The obvious answer is refactoring. That's what politicians promise in election campaigns and junior software developers demand when encountering a new code base. It's rarely ever done in practice because no one can disambiguate unnecessary from desired features and complexities. The second answer would be a clean implementation in some more formal framework (a statically typed language, a theorem prover, ...). That second solution often fails when attempted because the system is already unsound. Fortunately, no one cares about those "weird corner cases" and everything is left as-is until someone runs away with a million dollars or so.