remove self-closing tags in WordPress (unneeded if coding in HTML5) – insert into functions.php

remove_self_closing_tags

function remove_self_closing_tags($input) {
	return str_replace(' />', '>', $input);
}

add_filter('get_avatar', 'remove_self_closing_tags'); // <img />
add_filter('comment_id_fields', 'remove_self_closing_tags'); // <input />
add_filter('post_thumbnail_html', 'remove_self_closing_tags'); // <img />