Wow, I had no idea that so many women dug their fingernails into men's backs... I thought that only happened in the movies. I guess I've never done it... but I keep my nails plain and short (no polish or manicures, etc), so I guess they wouldn't hurt even if I did use them.
I do like to grab ktspktsp when he's on top, to hold him closer and pull him into me, but I don't use my nails because I know that would hurt!!
I just use my fingertips and press them into his back as I hug harder.
I wouldn't want him digging nails into my back either, if he had them. Maybe I'm just not into pain...