

It’s a giant white canvas, anyone can place a pixel once every 5 minutes. Obviously works way better when you are coordonating with 100s or 1000s of people. You can place the pixel anywhere, even if someone else put something there first - hence how the images changes or some groups come up with small animations.
For anyone concerned about traffic to reddit, the absolute best thing you can do is find ads next to “offensive” content and e-mail the CEOs and marketing departments of those companies saying you won’t use those products due to their ad placement on reddit. Literally nothing else will hurt them faster.