One of the common words I missed in in the vulgarized puzzle was virgule. The fact that only seven people got it doesn't necessarily indicate that it's not a common word as I would imagine that even if you know it it's not one that you would easily spot.
But I must admit that it's a new word for me - I never knew the 'slash' was called anything other than that. Lest all you polymaths hold up your hands in horror at that statement, let me say that although I consider myself to be reasonably intelligent I am, unfortunately, an uneducated person. This isn't a suggestion to downgrade it to rare, just a confession of my ignorance.