No evil meant or intended.
It makes port 80 of the origin server unavailable for all traffic that is directed at the hostname.
I don’t like the current tone of the conversation in this topic, so I’m unwatching it.
My opinion on Cloudflare in combination with Discourse can be summarized as “many people are apparently unable to configure it correctly so in general I would recommend against enabling it. If you want to use it for DDoS protection, then I would recommend enabling it with very specific settings only.”