That's an issue that would require a fundamental redesign of how our ignore system works.
1) Ignore Public posts by user x. 2) Ignore Public replies to user x. 3) Ignore (block) PMs from user x.
Plus, a global toggle of #1 and 2.
Personally, I'd like to see us go (back?) to that, but it's not a high priority at the moment. I know we used to have that level of control on SI, though some of it was lost in the '03 rewrite.