In the image below, you can see two rectangles with some text inside. If you take a closer look you will notice a difference in spacing between lines. The spacing between the first and the second lines is smaller than the spacing between the second and the third.

The last line is always separated. If you have 10 lines of text, the spacing between all the lines will be OK except the spacing between the next to last and the last line of text.
The font is the same (in every aspect) accross the lines (except the title), and there are no custom paragraph properties set.

Why does this happen and how to solve this?




Question: Extend Wordpress (4.x) session and nonce
Answer: Your problem is that you call wp_logout_url immediately after wp_set_auth_cookie. 

wp_set_auth_cookie() does some setcookie() calls. Unfortunately setcookie doesn't make the new value available instantly in the PHP global $_COOKIE. It must be set through a new HTTP Request first.

wp_logout_url() (via wp_nonce_url > wp_create_nonce > wp_get_session_token > wp_parse_auth_cookie) fetches $_COOKIE[LOGGED_IN_COOKIE] in order to create a valid nonce, not knowing that the logged in cookie has already been updated. (I'm not quite sure if we may call this a WP core bug.)

There is an action hook in wp_set_auth_cookie named set_logged_in_cookie, which should allow you to update the session cookie value during your ajax request. 

function my_update_cookie( $logged_in_cookie ){
    $_COOKIE[LOGGED_IN_COOKIE] = $logged_in_cookie;
}
add_action( 'set_logged_in_cookie', 'my_update_cookie' );