From a very practical standpoint - obfuscation and complexity also makes it more likely that the code will be broken in the future. Not broken like "discovered

From a very practical standpoint - obfuscation and complexity also makes it more likely that the code will be broken in the future. Not broken like "discovered and disclosed" but broken like: "it doesn't work any more". I mean - it's not like the unit tests are going to contain check_backdoor_works() (etc). So the simpler and more straight forward you can get your backdoor snuck in - the longer you can know it will remain, and keep working.