Unfortunately anything that doesn't seem like a trap can also be a trap, meaning that pretty much the safest way to proceed is to treat the entire world like a trap.
At the very least you can count yourself lucky IVAN doesn't have things like, say, pre-determined ambushes full of hideous creatures which trigger upon entering a certain tile or taking a certain item, or things like DoomRL's lever which turns the entire floor into lava.
Well unless we wanted it to, now that we kinda have dev up.
System would indicate in graphic if person is mounted on horse or not.
Same system also show if person mounted on boar, elephant, polar bear etc.
Or if person mounted on ass.
Ivan find mounting on ass funny.