Earlier quoted context omitted.
It's from this tos page: https://www.cloudflare.com/terms/ 2.8 Limitation on Serving Non-HTML Content ...Use of the Services for serving video or a disproportionate percentage of pictures, audio files, or other non-HTML content is prohibited, unless purchased separately... A huge text/plain artifact, requested often, would seem to fall into that category of "disproportionate percentage" compared to text/html served.
My best guess is that CloudFlare wrote this to prevent folks from serving big binary files like photo, music, or video and this txt file case was an unintended condition that happens to work to CloudFlare's advantage. text/plain though is decidedly not text/html and I would expect CloudFlare to potentially do some on-the- fly optimizations that are aware of the structure of an html file that save terabytes a day at t…
Some think its very Oracle of Cloudflare to do so. I do not blame them.