I think Reddit is a terrible example. The moderators are volunteers, the rules and their application seem entirely arbitrary, and there is no way to opt out.

The key point the author of the article makes is the difference between moderation and censorship: you can opt-in to see moderated content, but you're unilaterally prevented from seeing censored content.

What Reddit does (removing posts, comments, banning accounts) falls under the definition of censorship here -- within the platform itself, obviously.