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I think in terms of the processing engine, it would probably make sense to apply the NR first and then the sharpening, but in terms of workflow, I guess it isn't that obvious which should go first.
Jeremy,
In Lightroom/ACR, you have no control on the processing order of the different adjustments like noise reduction, sharpening, HSL, basic adjustments, curves etc… Because NR panel comes after (or below) Details panel, it doesn't mean that the Lightroom processing engine will use that order.