Normally when a user's post gets downvoted to a negative r-score, the post is hidden. This is not currently the case if a user's reputation is 65 or above. No matter how many votes a user with reputation 65+ gets, their posts will still get shown.
The idea behind this is that hiding posts was intended to prevent spam/abuse, and users who have earned a 65 reputation are not going to be spamming/abusing. In the rare case where a high rep user goes off the deep-end, the community can downvote them back below 65.
Unfortunately there has recently been a case where 65+ user's account was compromised, and this protection has allowed the malicious user to create posts and comments without fear of being hidden.
Since the protection against getting hidden is creating an exploit for malicious users to take advantage of unsuspecting users, I felt it was best to remove the protection.
I submitted a pull request to remove the protection for 65+ users:
If the pull request is accepted, it will mean that any user (regardless of reputation) can have their posts and comments hidden if they are downvoted to a negative r-score.