True, raw "sharpen" increases the noise but using the unsharp mask (in lowest effective setting 0.2) works as a "soft" alternative... after setting the autolevels. It also helps to bring up the white text "edges" on black dial for example. It depends on the picture but it usually improves the visual quality although it lessens the resolution.
Another factor to "noisiness" is that people save over compressed picture format (i.e JPG) over and over again... For most images there is _always_ some degradation from a lossless format like PNG or BMP to JPG, no matter how high you set the quality. But in practice, at the highest setting the degradation is not visible, if you only do it once (and use highest (10) quality). JPEG is mostly a problem when you open and save, open and save, etc., repeatedly. Much bigger factor than increasing picture sharpness once.