Canonicalization versus error-correcting codes; ideally, a programming language syntax should be such that the Hamming distance beteen any two valid programs is at least 2, for the same reasons that you want parity bits on RAM, even (especially) if you're trying to encode the data stored in that RAM in a way that makes every bit pattern a valid whatever-you're-encoding.

Edit: basically, communication from the programmer to the compiler is a lossy channel, and needs error-detection, but human brains don't do parity codes well, so syntactic redundancy is the way to go.