QR codes were the cause of me editing a post and deleting comments. I'd live blogged a session at work (back in 2007) about it and the speaker had complained about it, so work asked me to amend a couple of things, even though it was an open session. But then there was a comment war that just went on, as far as I could see between 2 groups who were looking to "own" it and make money. The original post is lost, (it was on blog network that no longer exists), but this was my comment at the time https://blog.bibrik.com/archives/2007/09/editing_posts.html