Ah, thank you. I misread the GP. It seems that he is saying nearly[^] exactly what I wanted to say in the edit. [^] the property should hold not only for singl

Ah, thank you. I misread the GP. It seems that he is saying nearly[^] exactly what I wanted to say in the edit. [^] the property should hold not only for single-bit changes, but all length-preserving changes -- it's perfectly fine for all single bitflips to e.g. result in invalid codestreams.