If you hover over the name of a category you see this:
but if you hover inside the teal-colored box but not right on the text you see this:
There was an earlier topic about this problem, but the participants in the topic thought the difference was about which browser you use, and they couldn't get reliable results.
I guess I should tell discourse.org about this, but meanwhile, we should just disable curly quotes maybe? That's a checkbox in Settings.