This only works if you put the special character in the beginning and not at the end e.g. if I type "hacker news %" it still only filters by open tabs, but it doesn't show the "Tabs x" label (whether I add a space or not). Which is how I use it 99% of the time, since I only need to add special characters if it wasn't already finding what I meant without them.

(Not that I mind personally, since I'm already familiar with the feature)