Could be both. There are other postings that have not been identified by who yet that could also lead to charges and divided liability.
You make a good point in that the article does mention possible charges against the people who set up the ‘confessions’ site in the first place. To me, that would be the more appropriate remedy for a charge.
Someone else had already made the charge against the teacher and Sagehorn was replying to it. Doesn’t make any of it right, of course.