It was more than one comment. We judge 'trolling' by its effects. Inflammatory posts on divisive topics provoke flamewars, and that destroys the commons.

https://hn.algolia.com/?sort=byDate&prefix&page=0&dateRange=...

This doesn't mean you can't comment on divisive topics. It means that as the topic gets more divisive, comments need to become more thoughtful and more substantive, not less.

When you decide that comments are "trolling" by their effects, rather than only their content, you give censorial power to people who respond poorly.