Source

File: wp-includes/comment-template.php

function comment_author( $comment_ID = 0 ) {
	$comment = get_comment( $comment_ID );
	$author  = get_comment_author( $comment );

	/**
	 * Filters the comment author's name for display.
	 *
	 * @since 1.2.0
	 * @since 4.1.0 The `$comment_ID` parameter was added.
	 *
	 * @param string $author     The comment author's username.
	 * @param int    $comment_ID The comment ID.
	 */
	echo apply_filters( 'comment_author', $author, $comment->comment_ID );
}