Source

File: wp-includes/comment-template.php

function get_comment_author_email_link( $linktext = '', $before = '', $after = '', $comment = null ) {
	$comment = get_comment( $comment );

	/**
	 * Filters the comment author's email for display.
	 *
	 * Care should be taken to protect the email address and assure that email
	 * harvesters do not capture your commenter's email address.
	 *
	 * @since 1.2.0
	 * @since 4.1.0 The `$comment` parameter was added.
	 *
	 * @param string     $comment_author_email The comment author's email address.
	 * @param WP_Comment $comment              The comment object.
	 */
	$email = apply_filters( 'comment_email', $comment->comment_author_email, $comment );

	if ( ( ! empty( $email ) ) && ( '@' !== $email ) ) {
		$display = ( '' !== $linktext ) ? $linktext : $email;
		$return  = $before;
		$return .= sprintf( '<a href="%1$s">%2$s</a>', esc_url( 'mailto:' . $email ), esc_html( $display ) );
		$return .= $after;
		return $return;
	} else {
		return '';
	}
}