Ideally there should be a way for user to decide if they want to create an account or not… So commenting out the code for the password will not be a good solution. Instead maybe a checkbox defaulted to ON with Create Account label, and display the password filed only when the check mark is enabled.
I just realized that by unchecking the Automatically generate username from customer email. in Settings the checkout form will now display Username field. Which makes the checkout process easier to understand.
I still think that above it there should be a checkbox which enables/disables account creation that would hide/display the fields. I think that would make it much more user friendly.