Removing the "Your comment" textarea or make it optional

Hi all,

My goal:
I want users just to leave their E-Mail address and Name below a post.
Please note: If possible I’d like to avoid plugins and external services like MailChimp.

My questions:

1. How can I remove the textarea?
2. Can I make the comment textarea optional?

I’ve searched high and low, but now I’m a bit lost if this is possible at all.

I stumbled upon some filters, but they always remove fields I’m not interested in ??

Example:

function remove_comment_fields($fields) {
    unset($fields['url']);
    return $fields;
}

add_filter('comment_form_default_fields','remove_comment_fields');

Thank you very much in advance for your time.
Oliver