I don't think that pure citational answers are a good idea, because of legal reasons (but IANAL):
All user contributions on Stack Exchange sites are licensed under CC-BY-SA (see the footer of this page). An user can only grant a license to content he created himself. I don't think that simply copying and pasting a few paragraphs of text and applying some formatting creates new content. This reasoning ins moot in two cases:
- The cited content was licensed under a compatible license, or
- The citation is small enough that it can be considered to be “fair use”. Note that “fair use” is an US legal term and does not necessarily exist at other locations.
However, any user who was considering to post a pure citational answer can easily build his own answer from that:
- Explain how the quote is relevant to the question and possibly give examples.
- Only quote the essential point and refer to the whole content, e.g. via a link or book title. This has to be balanced so that the answer isn't reduced to an equally bad link-only answer: Links can break, so the answer should still be able to be useful on its own without the linked content.
Citations should generally be marked as such, e.g. with “quotes” or a blockquote environment (in Markdown: start each line with a
>). The source should always be mentioned to make the quote verifiable and to allow a reader to explore the context of the quote. It is also a matter of honesty to mark the work of others as such.
The answer which you linked to as an example seems a bit borderline, but is actually OK. In case the answer gets edited, I am referring to the first revision (i.e. original answer).
- The content in the citation plus the large image is copied verbatim from Wikipedia.
- Wikipedia content is also licensed under CC-BY-SA, so the license is compatible with this site.
- The cited text is attributed in the form of the link to the Wikipedia page where it was taken from. It would have been better to unambiguously show which link the content was taken from.
- The citation is framed by a few sentences of explanation that show how it is relevant to the question. The answer would still “work” without the citation, so the answerer has created his own content here.
- Only relevant parts of the source were quoted, and all images were mirrored. Therefore this answer will stay useful even when the links break.
If we want to be really exact we could criticize that it isn't immediately obvious that the large image is part of the quote, and lacks correct attribution. This attribution could have been given implicitly by including the image in the blockquote or by linking to the image's page on Wikipedia. It is also possible that future revisions of the Wikipedia page remove the cited content. Therefore it would have been more correct (in terms of attribution) to link to the specific revision of the Wikipedia page.