De Rated, Band a Lot
The PPrune search function reveals that the same points were being made in 2006 with some suggesting dire consequences to the vacuum pump if rotating the prop backwards with others pointing out that rotating the prop backwards was standard practice when setting ignition timing, presumably with no damage to vacuum pumps.
For a specific set of circumstances: Cessna 172 with cold engine (first flight)- if we rotate prop backwards by hand is it possible to cause damage to engine or engine components ?