I was unable to respond directly through email. I will attempt to upload an example file here. Within this file, it can be seen that there is some geometry masked by a modifier. The problem is when trying to sculpt on the geometry that is shown, which is under the masked geometry. The file includes a generic model from the MakeHuman project and may be considered NSFW. Thank you, and apologies for the delay in response.

How are you checking the effect of sculpting ? The model after sculpting and disabling the modifier:

Checked in rB15670ebb9549db77414e266324d33114fa3af468 as well as 2.92.0

For example, when i attempt to sculpt with the mask hiding the geometry that is Not body, the vertices the sculpt brush registers on that i can change correspond to the mask, which is invisible, and not to the geometry i can see. So, if i try to scuplt on the chest, it will not 'snap' to vertices on the chest, it will snap to the hidden vertices of either the hair guide that hangs over the chest, or to the Tights-Helper. The vertices the brush registers are the hidden mask and not the visible geometry. So, when the brush marker lights up a vertex, it is a vertex that is not supposed to register because it is not even visible. trying to move over a vertex that is on the visiblebody does not change color because as far as the brush is concerned it is trying to sculpt on the invisible geometry that is masked. Ofcourse, if i make the brush big enough and strong enough it will affect the unmasked geometry, but this is not proper function, in my understanding. When geometry is masked, it should not be in the way, and the brushes should not be landing on its vertices instead of the visible vertices.

Thank you

Notice how the brushes selected vertex is floating and not the vertex of the visible geometry. It is floating becuase the brush has landed on a vertex of the hidden/masked geometry