Answers are not binary good or bad. There is a spectrum from utter crap to awesome essays. Our rules exist to ensure answers are more towards the latter than the former. How much more? That's subjective. We have guidelines in our rules for what a good answer is. We also mention what we consider bad answers.

The answer above does not meet any of our "bad answer" criteria (it's not a link, an anecdote, or speculation, etc.). The question then becomes how good it is? It's not very long, but it does address the question. If you read carefully, there's a reference to a book published by an university press in there, and another reasonable source provided later. So the answer is properly supported (we don't expect users to cite chapter and verse, though they get bonus points for doing so).

In short, we believe the answer meets our minimum standards. It's so great that I'd use it in a flair application, but it's good enough.

If you have any further questions about our rules and policies, please create a [META] thread or send us a mod mail, as such discussion is off-topic here. Thanks.