Okay, so this is so disgusting, but also comical looking back. My face must have been hilarious for its stunned disgusted look. As a teen, one weekend I spent overnight at my then best friends house. I had a mad crush on her older brother (2 years older than her). I woke up in the morning and went downstairs to the living room, I was last to be awake. When I walked into the living room, they were sitting on either end of the couch and honest to goodness, were literally chewing each others long toe nails off! Kid you not! Can you imagine a 15 year old girl and a 17 year old boy noshing on each others dirty feet fangs? I was so repulsed. They just cracked up laughing and said Oh we've always done this!!!! That somehow just repulsed me further.
In one of life's oddities, I haven't seen either of them since I was about 16. Well I moved this summer, and they live a block away on my same street. Apparently despite being 40'ish, they reside together. Somehow, that isn't surprising to me
I don't know that you can break people's quirky habits, even if they do seem very gross. I think you absolutely can draw the line on the part where hundreds of nails pile up under furniture!!!
Edited to add: The day of the Team Chew, my crush died a well timed death. The end. Never could see him in the high school halls kissing his flavor of the week girlfriend again without giggling and wondering if she knows he uses that mouth to nosh his sisters nasty toe nails