I'm seeing the following in SO since yesterday afternoon. I tried all the usual suspects...logging in and out, clearing the browser cache, restarting my browser, and even this morning, after restarting my machine (cold boot)...
If I go to edit a previous question, tools appear and formatted text window updates properly. This only appears to be happening with new questions. Other SE sites (including SO meta) are working just fine. There's no uproar about this on meta, so I suspect it's just some anomaly with me.
However, I'm baffled.