Dear Yenta,
I feel like there are two types of people in the world. Those who think it’s ok to trim nails in public, and those who do not. What to do when someone starts cutting his nails right next to me on the subway, in class, or even at a restaurant?
-Nails Are Nasty
Nail clipping in public is a form of defecation.
Dear NAN,
Wow. Well, for this it completely depends on the circumstance. Is this a friend or a stranger? Where do they leave their clippings? Is it done neatly, or is it quite obviously grotesque?
Some girlfriends and I once decided to give ourselves pedicures in the grass in Dupont Circle on a sunny day. That might have been gross in and of itself. But what really repulsed us was when a man who had not bathed in a long time approached us asking if he could use our nail clipper. He stood over us and clipped away, dropping nail chunks all around us. In that case, it was our nail clippage karmic return that we brought upon ourselves.
We gave the man the nail clippers for keeps and learned a good lesson about grooming in public. It is gross, and breeds grossness. What can you do in a situation with a stranger? Get up and walk away. If the nail clipper person is bleeding or leaving flesh/nail debris in a public place, like on a bus, you can notify the driver since it is a violation of health code.
It makes me think of when people pick their nose and wipe it on the subway seats. There should be a civilian elicited ticket that we can give people who smear their body excesses in public forays.
If it is a friend, just tell it like it is. “Hey buddy, you are being repulsive. Would you mind waiting to sever the edges of extremities when I am not attempting to hold my dinner down?” There are obvious nicer ways to say it, and it is not rude to ask someone to take care of their personal hygiene in private. Another example: public flossing. This absolutely disgusts me.
Walk away, state your case, or one up the mofo and start farting or picking your nose and when they scoff just look at them calmly and say: “You started it.” Boom. The end.
Your 29-Year-Old Yenta 
Thank you for addressing this issue! I have two co-workers who clip nails at their desks, and while the sound is annoying to me, they’re certainly not getting their crud on anything but their own workspaces.
ONE TIME though, years ago, I was on the subway and I saw a woman clipping her nails directly into her handbag! I thought it was pretty gross, but so unusual that I think I’ll always remember it.
Other issues similar to this for me – hair brushing in restaurants or other places where you do not want strands of people’s hair to get on you or your meal. And the biggest of all for me probably – people who think it’s okay to spray perfume in an enclosed space (like an airplane for instance) – GAGALICIOUS