I don't know whether this just started or perhaps it's actually something new in my browser, but it must come down to SE code ultimately and I've never noticed it before today/yesterday.
Submit a comment via the "Add Comment" button, or submit a close-vote, or post a question, or do anything really that involves clicking one of those kinds of buttons, in Chrome 48 on Windows 7 64-bit, and you'll see your mouse cursor very briefly turn into the "not allowed" cursor right before the button is removed.
It seems the button is being disabled or whatnot before it's being hidden, which results in this "flash of malstyled content". Not a big deal but a little annoying.