If you spend time watching /r/place you see that pictures mostly form in a natural, progressive way. This is the only place you see hundreds of pixels being changed uniformly all at once. Even bots would be making more gradual changes than this. It's clearly someone who has a brush tool for censoring.
The admins are blatantly censoring the drawing, putting checkerboard squares or circles of random color over that part. Here are some screenshots I took only seconds apart.