Yes, more obvious now. I do find it peculiar that a sharpening algorythm should pick up noise that has already been "reduced", but your evidence seems to point that it may. This must mean that the noise reduction is not adequate for certain edges to remain invisible to the sharpening. But then, if one reduced the noise even more (i.e. pushed well beyond the defaults) one may begin to impair desirable detail even with capture sharpening. Careful compromises!
I'm not surprised.
Noise reduction software doesn't remove noise. It makes it less obvious. It can be accomplished in a number of ways, but the essence is the reverse of sharpening. Neighboring pixels are examined to determine whether the values for a pixel are significantly different *WHERE* little variation is expected in terms of color and/or luminosity. The contrast between those pixels and their neighbors is reduced.
The Median filter, for example, is a fairly blunt tool for noise reduction. The neigboring pixels are consulted and their median value (sort the values and take the middle value) is used to adjust the pixel. This "smooths out" variation and reduces noise.
Sophisticated tools like NeatImage, Noise Ninja, and Noiseware have more sophisticated algorithms for determining noisy pixels and for replacing their values, but in essence they reduce contrast between noisy pixels and their neighbors.
Sharpening software can still detect the contrast between noisy pixels and their neighbors *AND* emphasize the contrast, undoing some/all of the noise reduction.
That's why I refer to noise reduction and capture sharpening as antagonistic in my eBook and my video on sharpening.
You can reduce noise to the point where capture sharpening cannot make it more visible. The resulting artifacts -- a plastic-like appearance from loss of significant details -- will likely be worse than some residual noise.
If you do not use layers masks, capture sharpening and noise reduction will largely cancel out. Depending which is more aggressive in effect, you will either end up sharpening noise or softening significant details.
Capture sharpening is best done with a layer mask that restricts sharpening to the edges. ACR and LR now include some edge masking. Focal Blade and Photokit Sharpener give you direct control over edge masking. So do my actions and scripts (there are free actions and scripts for noise reduction, masking, and sharpening on my site).
I strongly recommend noise reduction on a layer and using a surface mask to keep noise reduction away from the edges. That will allow you to use more aggressive noise reduction settings in many cases without losing significant details. That can make it less likely for noise to reemerge after capture sharpening. I have a free script that can automate the generation of surface masks. There are even options to limit the masks to tonal/color ranges (e.g., the shadows).
It takes more work, but if you can restrict noise reduction to just the features where it's most needed, like the shadows, you can be more aggressive with the noise reduction settings. Restricting noise reduction was the #1 motivation behind my masking script.http://www.thelightsright.com/TLRProfessionalMaskToolkit.htm