...that the down vote storm is actually a Watson AI bot? It's pretty primitive AI technology but it could be trained on a lot of posts to decide good/bad. It never appears to up vote any post which would make sense with old AI (you don't want to trust it to endorse something just in case but it's always safe to down vote.) Obviously, it is not modern enough to be "conversational" (its strength is answering quiz show questions). It doesn't look like Watson bot ever posts anything. Which would again be consistent with a slightly archaic AI system with limited functionality.
That would explain why the down votes are regular and sometimes instantaneous. Most humans would tire of constantly monitoring the forum. But a Watson bot never needs to sleep. Also, it might even be able to be trained to raise an alarm if it thought a post was really negative.
I'm obviously speculating but the down vote storms are curious and the number of down votes often don't seem to be reasonable.