It all depends on the algorithm used behind the scene. Why would 1 downmod + 1 upmod = 0? Calling them up/down might be part of the framing issue that we're stuck with since the reddit days.

Fun property of a system with upmod and downmod: If every user mentally assigns a target score to a post (eg.: that comment should be worth 7 points) and votes always in the direction to reach the target, then the resulting score will be the median of all the targets. Statistically. That seems like a desirable goal, so maybe one should encourage people to vote that way.