Some sort of blocker for stopping people from sitting. The reason for this is stuff like trenchwars. There's the sit and press shift glitch. The game thinks your crouched, but people see you sitting, so the hitbox is messed up. It can ruin a game on trenchwars, since the guy doing the exploit can still shoot at you.
If no one wants to do it but knows how, tell me I'll give it a shot.