comments-content.php

/**
 * Adds comments just before content, nothing between them
 */
add_filter( 'the_content', 'bf_comments_content', 10);
function bf_comments_content( $content) {
	if( is_single() && comments_open() ) {
		ob_start();
		comments_template();
		$comments = ob_get_contents();
		ob_end_clean();

		return $content . $comments;
	}
	else {
		return $content;
	}
}