<p>I think an answer that only copies and pastes from Wikipedia, with appropriate attribution, is fine if it answers the question completely. Originality is nice, but shouldn't be required. I believe Wikipedia's license is compatible with Stack Exchange's. Copying and pasting more than a few sentences from sites without free licenses could be legally problematic.</p>

<p>Any answer to a question, even a very short one, should be posted as an answer rather than a comment, because otherwise Stack Exchange can't recognize the question as answered.</p>

<p>Here's <a href="https://stats.stackexchange.com/a/224790/14076">an example of an answer I just wrote</a> that's basically just a copy-and-paste from Wikipedia.</p>
