When I was taught to drive, I was told that "slogging" the engine - open throttle at low RPM, e.g. 1000 RPM - was bad for it. Particularly when driving up a hill as that means you'll be stuck at that RPM for longer. It'd "wreck the engine" and all that.
I've been thinking about this recently, and can't see why it would be, unless the timing of the engine was poorly designed for lower RPMs. That doesn't make sense to me, given cars happily idle at 700 RPM.
Maybe it's not good to have a full-force explosion without the cylinder moving quick enough to quickly exhaust the pressure, might lead to high pressure and heat for too long a time period.
Though these are just my technical musings. So does it damage the engine?