In the Mana Temple came across a "friendly" gnoll in the traps area. I noticed that when I swapped places with it other monsters didn't seem to move; checked the turn counter and indeed no turns pass however many times I swap back and forth. Not sure if it's swapping *to* or *from* a trapped square that does it (or, I suppose, some other factor that I'm missing). Testing in exploration mode I wasn't able to reproduce the behavior on a normal level with a companion or a random non-hostile. I wonder if it has to do with the effective "trap immunity" that monsters sometimes have (where they won't trigger traps unless frightened or stunned etc.).