I don't use Cloudflare.
The list of popular hosts changes on a yearly basis, much like the list of popular social media sites. It would be unreasonable to ask the MyBB team to provide this kind of support for every possible host.
I wouldn’t like to see this in the core. Would make a pretty good plugin though.
Cloudflare can cause its own problems. I don't think that will be a good thing when it is included in the core.
8% of all websites on the internet use CloudFlare. This is bigger than Amazon and Akamai!
The setting in AdminCP will simply be:
IP Address: [ Default ] [ CloudFlare ]
Which means 92% does not.
Cloudflare is really a new service, but it will be just a waste of time to add it as a core feature