Oh, Lord.
I agree that independent citations are a good idea, in general. And making stuff up is normally a bad idea. But given the range of questions that get asked, I'm not sure how to formulate a hard and fast rule. As an example, I was asked to contribute to this thread as a result of my answer on How can I ask "What's up" in aristocratic style?How can I ask "What's up" in aristocratic style?
And yes, I made it up. But there are at least two levels of justification.
The first is that, for citations I'd need to quote from one or more novels from "the beginning of the 19th century". And to be honest, that's going to be hard.
The second is that the OP started with "I need to write a letter in an old manner". Note that it's unlikely he needs real period authenticity. Rather, he needs only to suggest it in a form which is in keeping with modern stereotypes of how people spoke at the time.
So, I generated a response which seemed likely to agree with folks' stereotypes, as I figured that would more directly fulfill his needs than a possibly more accurate but less satisfactory response would.
I guess the point I'm trying to make is that there is a continuum of citation needs, with questions like that one, or those dealing with shades of meaning, getting a more lenient treatment. (Hmm. Should I post a question in ELU asking for a one-word term for "citation needs?) And I'm not certain what the policy should be. I'm inclined to be somewhat liberal, with corrections from other members if responders start getting too lazy.