Parts of the board are being protected by bots. You login, sideload some JavaScript into your browser window, select the region to "defend", and leave it open. Every 5 minutes it checks the defined area, and if any pixel mis-matches, it uses your tile-placing slot to repair it. There's also a browser addin that will let you see an image overlay template, and you can manually fill in any tiles.
Some boards started off with bots, like the pink Osu! circle. Others started organically and resorted to bots when they got butthurt about being erased. 4chan tried to bot the tranny flags into all black, and the mods got the script yanked off GitHub.
xQcOW, the streamer from last night, used 200k Twitch viewers to do organic blackouts and vandalism. He could tell in real time which places were botted and which were organically defended, by how fast they undid his vandalism. You could also tell the mod edits (black square over 2B's ass) because it was done instantly and had no user names attached.
His stream is worth watching, because at some point redditors come into the chat and cry that he's "using his platform against small communities", and he replies "so what?" Dude got superchats of people begging him to leave their flag alone, and got actual death threats.