I don't know how it works for you on you all's side of the pond but here in the U.S. "polarity" does matter. Here, AC plugs have two fat prongs and many have a third, round prong. One of the flat prongs is smaller than the other. The smaller one is the hot side and the larger one is the neutral. When there is a third, round prong, it is the ground. If the flat prongs are parallel, the plug is rated for up to 15A. If the small flat prong is 90° to the larger flat prong, the plug is rated for use in a 20A circuit only. A 20A socket may have the slot for the small prong 90° from the larger slot or it may have a T shaped slot that will allow both kinds of plugs to be inserted. Only three prong sockets are permitted anymore. Also, standard house voltage is 120V.
Technically, it isn't polarity since AC switches direction back and forth; here, it is 60HZ or 60 times a second the current will reverse then turn back again. However, since the neutral line eventually is connected to ground, to avoid dead shorts, it is critical which side of a plug gets connected to the hot side.
I know this is an old thread, but I received an email asking for a comment from me.