You're missing the point that we are not talking about downvotes of specific comments, but downvotes of most comments by an user.
There is no reason -- absent rules -- that couldn't extend to all of a poster's comments if you want to see fewer comments by that person.
Below is a message I just got from jackk. Some specifics have been redacted 1) so that we can discuss general policy rather than the details of this specific case 2) because presumption of innocence, just in case there happens to be an innocuous explanation to this.
So... thoughts? I have mod powers, but when I was granted them I was basically just told to use them to fight spam; there was never any discussion of any other policy, and I don't feel like I have the authority to decide on the suitable course of action without consulting the rest of the community.