From my reading, this "hand out a 2xx and an error message" advice is for badly behaved clients who are retrying when they get 4xx.
It's not what "should" be used, it's what the author found to be effective.
It's not what "should" be used, it's what the author found to be effective.
But trying to handle clients who mishandle things like that is a fools errand. What client, in their right mind, would try to retry a request that is failing because of what the client is sending? In no case does that make sense, ever.
Similarly, should everything just be 200 then just in case clients mishandle redirect requests?
People will copy random snippets from SO and smack them with a hammer until they seem to work then move on to the next thing. I've seen some incredibly stupid code out there, code I can only assume the author either didn't understand or truly didn't give a fuck about. Probably both.
Sure, I agree a lot with this, but that doesn't mean you and me should also do idiotic things. Lets just return correct status codes and the ones who misuse it, will misuse it :)