Earlier quoted context omitted.
I tried to split the difference with my April Fool's RFC, which proposes the HTTP status "397 Tolerating" for when you want to say "yeah, I know what you want, and I'll give you that, but here's how you were supposed to ask for it". https://pastebin.com/TPj9RwuZ
I am borderline sad that this is only an RFC. The number of services I use that I wish had a "warning" side-channel for letting me know something in my query was off, let me tell you...
In fact, it's the recommended way to do things like tell a client things it might need to know. Example: "The game servers will be shutting down in 15 minutes for maintenance."