Wear on an IGH by pre-selecting gear under power I have a bike with an 11 speed alfine IGH in the rear wheel.  It works fine, and I am comfortable riding it.

When accelerating hard or sprinting for some reason, I've noticed its possible to change at the shifter but the gearbox doesn't react until the chain tension drops for an instant.   For the Alfine, this mostly happens when changing to a harder gear.

This is similar but opposite to a derailleur-equipped bike, where changing down to a lower/easier gear (ie chain moves to a bigger rear cog) needs a brief window of lower chain tension to get over.  You might have done this when on a climb and have run out of leg in the current gear, and need to change to an easier gear.

Question: Is this bad?  Is it causing more wear on the internals of the IGH?   

It seems my carefully-cultivated smooth pedal circle doesn't help.  A slightly choppier or bouncier pedal stroke allows the gear change to happen mcuh easier.

As a test I managed to ride in second gear  while clicking through to about 9th gear, though this was intentional.   When riding for real it might be only one gear postion out, but pulling away from a light quickly might cause 3~4 gears difference and when it does catch up I can end up in an overly hard gear,
Shimano IGH use springs to move cogs away from the cable pull, and what's happening is that lateral friction between the engaged cogs inside the hub is too great for the spring to overcome.

This is actually a good thing, because if one of those cogs slid sideways under power the load on the engaged remaining width of the cogs would steadily increase (same load, less engaged width) and very likely something would fail - you would chip the corner off one of the teeth on one of the cogs. Doing that isn't a problem, once. But over time you end up with a collection of hard chips of metal from the cogs floating round inside your hub. Some will inevitably end up on the wear surfaces of the cogs, or if they're especially large even wedging them so they don't rotate.

The reason you should try to avoid this is that you're not 100% reliable at keeping the cogs engaged until you back right off on the power. Every time it shifts just before there's no pressure on the pedals you run the risk of damaging something.