comment_form function in 3.0 was a good idea, but seems to be only partially implemented. There's no simple way to control classes in form elements. Also, if you want to adjust the markup for styling the form differently, you basically have to replace the entire field with the
comment_form_default_fields filter. If I want to encapsulate the label and required flag in a
div, and the
input in another
div (in order to float or position them), I just have to replace everything. Why not some more granular control that allows theme developers to choose the high-level markup structure, but without having to recode every part of the field's markup?