I did. My Sunday School teachers used to tell me that they were for punishment. That a monk who broke the rules had to sit on the misericord so that everyone would know he'd misbehaved. Like being made to stand on your chair in class.

Interestingly, a 'misericorde' (different spelling but carrying the same connotations of mercy) is a long, thin dagger carried by medieval knights and used to give the coup de grace to a defeated opponent. The idea being that it could be slipped through a gap in the armour to provide a quick death to a mortally-wounded man.