In an internal study (in an enterprise level) and assuming this is HTTP/1.1, that some proxies will either cache only brotli and made it inaccesible to gzip-only clients (even when you bothered with Vary, because they're plain broken in that regard) or just barf with it and time-out not only that particular request but crash a proxy.
The problem for large-scale deployment is that there are transparent proxies in Timbuktu (literally) since data is not cheap there, they need to use HTTP proxies to compress that, not to mention dial-up users in the US! (Good luck, Verizon!)
Or is Moonchild suggesting that Cloudflare is specifically trying to damage Pale Moon by not supporting its unique feature of Brotli over HTTP? That seems unlikely, insofar as it would require them to have an opinion one way or the other about a browser that nobody uses.
Sounds to me like they overestimate they own importance to CF a bit.
Nothing to see here.
Unfortunately, Cloudfare sides with Firefox and Chrome and does not offer Brotli on HTTP, citing old studies of proxies breaking when exposed to Brotli. They are also telling the author to go away in corporate-speak. The author, however, is unsatisfied and asks:
> What is the real (undisclosed to me) reason they won't consider even the possibility of Brotli being enabled for clients who support it? ... I can only conclude there's some agenda here that I'm being kept in the dark about...