Customize comment_form() beyond CSS, forms and labels

Hi,

In the recent two weeks, I have been struggling while trying to customize the comment form.

I don’t know PHP, and since everything comment form now resides in a function, having to deal with actions, hooks and just the core of WordPress in general is a source of great frustration when I want to do more than relatively shallow customization.

I’m hoping to find a comprehensive explanation on how to do the following, strictly without relying on the use of CSS:

Rearranging anything outputted by the comment_form() in relation to each other, eg. displaying the submit button between the textarea and the reply title.

Adding various custom elements inside the comment_form(), not just more input fields, eg., the avatar of the current user, additional paragraphs or the comments_popup_link() (or similar)

Is the above possible? If yes, can someone please explain how to do so, preferably with supporting examples.

The following is a short list of the most relevant methods I have tried. None of them have successfully covered anything beyond changing labels and adding custom input fields.

http://wordpress.stackexchange.com/questions/50593/how-to-rearrange-fields-in-comment-form

http://wordpress.stackexchange.com/questions/63247/how-to-change-the-order-of-elements-in-comment-form

http://wordpress.stackexchange.com/questions/23273/changing-position-of-cancel-comment-reply-link-and-other-elements-of-comment-for

http://wordpress.stackexchange.com/questions/39704/change-order-of-comment-fields

http://chipcullen.com/altering-the-comment-form-in-wordpress/

http://ottopress.com/2010/wordpress-3-0-theme-tip-the-comment-form/

http://justintadlock.com/archives/2010/07/21/using-the-wordpress-comment-form

Thank you