Yeah, probably not recommended, but I have to say that I do it all the time with black lipsticks and black eyeliner... I would think that the greater problems could result from using the pencil on your eyes after it's been on your mouth, actually, so as long as you sharpen it well before using it again, you should be fine.
I really have to get my hands on some of these Nyx shades. I'm loving what I've seen thus far, especially this colour. Looks gorgeous on you.
I decided to thumb my nose at a very grey day today and wear my favourite bold, warm red- Guerlain Genna.