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.
The only time I tried this I quickly gave up, because the poster I didn't want to see used the monthly quotes threads to karma boost. A malicious user that's intelligent can pretty much troll however they want and still have positive karma simply by copy/pasting quotes into the the quote threads.
This doesn't really apply to the topic at hand, but the quote threads are a serious karma problem, because they provide an effort-free way to generate huge amounts of karma.
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.