I don't know in VM 1.1 but I imagine that the solution I found for VM 1.0.x works there as well.
You have to modify the ps_checkout.php and account.order_details.php and substitute $db->f("customer_note") with $db->f("customer_note", false);
In this way the string fetched from the DB keeps the slashes (by default the f method removes them).
Then instead using preg_replace("/\r\n|\n|\r|rn/", "<br />" $customer_note) use str_replace('\r\n', "<br/>", $customer_note)
Remember to use single quotes and not double quotes in str_replace!!!
Bruno