This is a perfect example of where, if you go beyond just the superficial, simplistic understanding and definition of something, you'll run into trouble if you don't have a more complete picture.
A "conductor" is actually a rather vague term. If you think about it carefully, practically EVERYTHING is a conductor, even an insulator. If you have a good-enough current detector, and if you apply a high-enough voltage, even an insulator will "conducts".
So the question is, how do you categorize something, and when does it become "good", as in a good conductor? In solid state/condensed matter, we don't typically consider whether something is a conductor or not, but rather if something has a "metallic" or "semiconductor" behavior, because both of these can be characterized rather unambiguously (an typical (band) insulator is just a semiconductor with a huge band gap). What we do is we look at the dependence of the resistivity with respect to temperature. If the resistivity increases with increasing temperature, we say that it has a metallic behavior. If the resistivity decreases with increasing temperature, that is a semiconductor behavior.
This characterization is useful especially when we deal with more exotic behavior of a material, such as when the material actually changes from metallic to semiconducting as you vary its temperature (see, for example,
this.) So if we apply this understanding to "space", where will it fall under? Is the question even meaningful? If it isn't, then is the MORE complicated question on whether it is a superconductor or not even makes any sense?
As has been alluded to in this thread, a "superconductor" is MORE than just a conductor, or a conductor with zero resistance. The Meisner effect ensures of that. There are added criteria for something to be called a superconductor.
Zz.