From another conversation elsewhere, I bring you: The Prompt of Afterlife Porn. It wasn't really voices Harry heard behind the Veil while in the Dept of Mysteries. It was the Post-Lifer's Swingers Convention going full-swing, so to speak. Had he looked behind it, he would have been shocked to see his parents involved in quite the flexible threesome (or moresome). With the closing of canon, there are a LOT of characters who can join in the fun.