Cloudflare is already compressing markdown, but only with the type text/x-markdown, however since 2016 there is RFC 7763 so text/markdown should be used for markdown content.
This can be an issue since the first results for “markdown mime type” are already suggesting the correct type and people can easily miss the fact that it isn’t going to be compressed by Cloudflare.
So I’m proposing to add text/markdown to the supported content-types.