is it possible to render a stroked curve, in the same way that a vector program such as illustrator, or the paint operator in combustion, would stroke a curve with a 'brush', without actually giving the curve any kind of depth?
To my knowledge you'd have to create some kind of surface or object out of that curve to be rendered. Remember MAYA is a 3D environment and so the render cameras only see things that take up space. Points are infinitesimally small representations of a single coordinate set in 3D space that cannot be seen (consider a location on the earth - the location itself is a reference and doesn't actually exist even though we can point to it), and curves are essentialy infinitesimally thin connections strung between these points. Neither are visible objects. If it helps to think about this in relation to vector-based 2D software (like Illustrator), the curve there is infinitesimally thin as well. You're not actually seeing the curve, but the brush stroke that is being traced over it - like a pencil drawing a line on paper. The line is always there, but you don't see it until you add graphite to the paper (well... maybe that's getting into a little too much philosophy). Anyway, I hope that helps in some respect.