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with the settings as they are left. I never reset them to zero and as I don't see a history state that says anything about sharpen as I move from one image to the next. I suppose it is not applied.
If you mean when moving from one image to another in a folder that's open, things will go back to LR's default settings provided there was no preset applied at import. I think this is 25 for sharpen amount. I can't remember offhand since I apply a preset at import that adds more. It's been a while since I did one at default. Every raw file needs at least a little sharpening applied.
That said, 25's a good default so you might decide to leave it on that - it's not just compensating for soft digital capture, but also for the demosaicing algorithm that Lightroom uses. It's not doing heavy duty sharpening.