Frequently abilities can still be "in flight" and hit folks around corners. I've personally seen a BLM cast sleep on a BRD who is 3-5 steps around the corner on the opposite side of a wall as a BLM, and have that sleep hit. Presumably he started the sleep cast before the BRD was around the corner. This is just kind of silly. It's even sillier because I've also seen a SCH run around a corner, start casting Adloquium, and have their cast be interrupted by a BRD's Heavy Shot... when that BRD is on the opposite side of the wall.