Earlier quoted context omitted.
HN should limit the rate of comments per user per post. This user is seriously worked up to mute this discussion and spams in every comment thread. Edit: this user wrote 26 out of 88 comments here.
HN already has a rate limit. You get the message "You're posting too fast" when you exceed it. Though I think it's also tied to karma and might not trigger when all those comments get upvoted. And if you try to downvote them all, you'll run into the protections against mass-downvoting. Tuning the feedback loops to encourage good discussions while damping flamewars is a difficult problem.
The basic new account rate limit and the one you get from getting downvote quickly are too weak to stop what they are complaining about.