I was working on a particle Hair of a character and I was in Particle Mode with some of them selected.
So I did a copy/paste (Cmd+C/Cmd+V on mac) to see if I could duplicate those particles.
Apparently nothing happened and I continued to work on it.
Later I realized that I had got a full new copy of my figure, with a new armature, new materials, particles and all its stuff, and that I was actually working on it, rather than on my original object.
I don’t pretend that the copy/paste has to work on particles, but I find wrong that objects get copied when in Particle Mode.