Well you finally got wind of my block suggestion, but hope you realize some features are impossible in a decentralized system.
Instead of being able to block specific users from posting a comment that references a blog post (which I think alternative clients would find a way to subvert anyway, by embedding data, i.e. bottom-up supply & demand will drive features not top-down desires), the correct way to design such a feature is probably to allow the blog author to mark specific comments and/or usernames, which clients can optionally agree to hide. Again all power must remain with the individual users and no blog author should (nor in theory can!) be able to block a user from posting a comment.
mute already does this.
No it doesn't give the blog author the power to recommend to readers a blocklist for his/her blog posts.