Actually--they will hit the side of the tank if they feel cornered or trapped. Here's another article about them--scroll about halfway down, and you'll see the tale of this particular mantis 'escaping' from the critter keeper quite easily, and there's a pic of the author's finger after a close encounter.
http://reefkeeping.com/issues/2004-03/jf/feature/index.htm
http://reefkeeping.com/issues/2004-03/jf/feature/index.htm