More than once lately, when I've composed a reply in the standard editor window and clicked on the 'Post Quick Reply' button, I've been re-directed to the 'Advanced' editor window (with the text of my reply still intact), seemingly as if I'd clicked on the 'Go Advanced' button. And with the same click, my reply got posted to the thread anyway (verified this by opening another tab in my browser and seeing my new post in the thread). I could see how this could result in a lot of double posts, if one assumes they just clicked the wrong key and hit 'Post' again. The first time I saw this, I assumed I'd just drifted a little too far with the mouse, and clicked the wrong button. But after the 2nd or 3rd time, I'm reasonably sure it's not me.