I'm even guilty of writing client code that just retries on failing to parse the response, precisely because the server I was working with randomly would return

I'm even guilty of writing client code that just retries on failing to parse the response, precisely because the server I was working with randomly would return empty/corrupt responses for no discernible reason (it was actually Amex's API sandbox). Come to think of it, perhaps it was trying to rate limit us, as it happened a lot running our integration test suites! But the fact it returned 200 and even text/html as the content type was a bit ridiculous.