While it's true that buyers like to see the mark of an artist in brushstrokes and texture (especially in this age of multiple offerings in the form of prints and mold copies), no one likes marks left that look like obvious mistakes.
So what degree of craftmanship should be offered? What marks are acceptable?
A lot depends on the style of work you are doing, taken on an individual basis. A palette knife painting shows lots of textural marks, but if two colors overlap and make mud, it's still mud and detracts from the work. An elliptic form that goes out of shape is plain out a mistake. In sculpture, especially, there are a lot of decisions to be made.
Robust smears of clay can be powerful but the idea is to capture the energy of creating, not say 'I'm done' at 1/2 finished ugly stage. Flow is important. Usually fingerprints and scored sanding marks are sanded away, but there are times both are allowable in a limited way. A figure sculpture should have no fingerprints and if any scores are allowed to stay they should be faint and only visible on close inspection...then it's more of a discovery of your work process, and an interesting side effect.
Unless you are doing an abstracted form, any representational work needs to have accurate measurements, buyers have eyes and can easily see distorted limb lengths, uneven sides and features out of alignment.
There's a little more room for this sort of thing in obvious craft type objects, like hand sculpted pots...human hands are not calibrated machines. But bumpy is not the same as a hint of out of round. Question whether a rough area left showing is about a process you want to share or just showing a limit of your abilities.
The final answer to this is to create every single piece to the very best of your abilities and technical skill. Set aside time at the end to go over a piece, looking at it from every angle, to be sure that it's what you want sent out into the world as a representation of your vision. Good craftsmanship will give your work more value in the end.