customize comment form

This code will allow you to customize the comment field labels and will move the comment form below the fields. Add the code to your functions.php or to a plugin.

To change the labels, modify the Name CUSTOMIZED, Email CUSTOMIZED, and Website CUSTOMIZED, and Comment * CUSTOMIZED text.

/**
 * Customize comment form default fields.
 * Move the comment_field below the author, email, and url fields.
 */
function wpse250243_comment_form_default_fields( $fields ) {
    $commenter     = wp_get_current_commenter();
    $user          = wp_get_current_user();
    $user_identity = $user->exists() ? $user->display_name : '';
    $req           = get_option( 'require_name_email' );
    $aria_req      = ( $req ? " aria-required='true'" : '' );
    $html_req      = ( $req ? " required='required'" : '' );
    $html5         = current_theme_supports( 'html5', 'comment-form' ) ? 'html5' : false;

    $fields = [
        'author' => '<p class="comment-form-author">' . '<label for="author">' . __( 'Name CUSTOMIZED', 'textdomain'  ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' .
                    '<input id="author" name="author" type="text" value="' . esc_attr( $commenter['comment_author'] ) . '" size="30" maxlength="245"' . $aria_req . $html_req . ' /></p>',
        'email'  => '<p class="comment-form-email"><label for="email">' . __( 'Email CUSTOMIZED', 'textdomain'  ) . ( $req ? ' <span class="required">*</span>' : '' ) . '</label> ' .
                    '<input id="email" name="email" ' . ( $html5 ? 'type="email"' : 'type="text"' ) . ' value="' . esc_attr(  $commenter['comment_author_email'] ) . '" size="30" maxlength="100" aria-describedby="email-notes"' . $aria_req . $html_req  . ' /></p>',
        'url'    => '<p class="comment-form-url"><label for="url">' . __( 'Website CUSTOMIZED', 'textdomain'  ) . '</label> ' .
                    '<input id="url" name="url" ' . ( $html5 ? 'type="url"' : 'type="text"' ) . ' value="' . esc_attr( $commenter['comment_author_url'] ) . '" size="30" maxlength="200" /></p>',
        'comment_field' => '<p class="comment-form-comment"><label for="comment">' . _x( 'Comment * CUSTOMIZED', 'noun', 'textdomain' ) . '</label> <textarea id="comment" name="comment" cols="45" rows="8" maxlength="65525" aria-required="true" required="required"></textarea></p>',
    ];

    return $fields;
}
add_filter( 'comment_form_default_fields', 'wpse250243_comment_form_default_fields' );

/**
 * Remove the original comment field because we've added it to the default fields
 * using wpse250243_comment_form_default_fields(). If we don't do this, the comment
 * field will appear twice.
 */
function wpse250243_comment_form_defaults( $defaults ) {
    if ( isset( $defaults[ 'comment_field' ] ) ) {
        $defaults[ 'comment_field' ] = '';
    }

    return $defaults;
}
add_filter( 'comment_form_defaults', 'wpse250243_comment_form_defaults', 10, 1 );