Dropping a 1911 slide on an empty chamber shouldn't have any effect on sear engagement, unless the hammer falls to the half-cock notch. Even that would probably take multiple incidents to cause any damage.
The hammer
shouldn't drop on a dropped slide, especially if the gun is held tightly. It's more likely to let go if you hold it loosely--even then, it SHOULD hold.
IMHO doing ONE empty chamber slide drop a year or so is a good way to make sure you have good sear engagement.
Also IMHO, the empty chamber slide drop is more damaging to the barrel locking engagement surfaces.
I don't do it repeatedly, but I don't get bent out of shape if it happens. Again IMHO, it's MUCH less damaging to the gun than flipping the cylinder of a DA revolver out even ONCE. (Or dry-firing a P.38, but that's another story.
)
Oh, almost forgot--the EC slide drop is also hella hard on old-school oversized front sights that have only been staked in, GI-style, but almost nobody does that anymore. It also doesn't do any good to S&W adjustable revolver sights on a 1911 slide--a popular modification in the '70s--but almost nobody does
that anymore, either.