Some
mods have been designed to prevent reverse insertion of the battery by building a little nub that the battery nipple goes into. Without that nipple, the
mod wouldn't fire, because it wouldn't make contact.
My provari has it, for example. Because I imagine that reversing the polarity through the circuit board would be a bad deal.
In a mechanical
mod, it shouldn't really matter. You hear the center post referred to as the positive pin, but atomizers don't have polarity, and mechanical mods don't really either.
So the answer to your question is.... It depends.