behaviour vs comments

okay, behaviour driven development is nice, but it's not a replacement for comment driven coding. what i'm talking about is driving the code by beginning with comments,

// register user

    // validate details

    // check existing username

    // create user

    // send activation email

    // return success / failure

then writing the code that actually does it, keeping the comments. this way, you've already planned before you code without doing anything messy, and you have a contract that you can verify with your eyes, which is the biggest problem that coders have. yes, BDD is a good idea as well, but it doesn't make comments any less important. especially because BDD doesn't say why x.should.be.y

[wikipedia] and [anorgan's blog]