In third person view when prone on the very top roof of a fire station, if you lay next to the low wall and turn character so legs and feet turn towards the low wall, your feet will go straight through the wall and can be seen on other side. So there is no collision with feet or they are clipping through the wall (sorry can't remember which one it is classed as.)

Have uploaded a screenshot aswell.

This is on stable build 0.33.114926 {F30069} {F30070}