There seems to be relatively new functionality in math.SE: an ability to cite questions and answers. It includes the title, author, and a url.
How does this work in the various edge cases: unregistered guest, deleted user, community wiki with multiple authors, etc. ?
The feature itself is not new: the site had "cite" link for years, located in the dialog invoked by the "share" button. The change, which occurred around Sep. 11 (see announcement on MO) amounts to moving the link one level up, next to "share".
The functionality itself is unchanged, but since you asked about edge cases, here goes.
Nothing is different for unregistered users. The unregistered status, after all, is just a detail of their authentication workflow. Here is an example:
@MISC {1444207,
TITLE = {Finding the volume of a Tetrahedron},
AUTHOR = {Jackie (http://math.stackexchange.com/users/272604/jackie)},
HOWPUBLISHED = {Mathematics Stack Exchange},
NOTE = {URL:http://math.stackexchange.com/q/1444207 (version: 2015-09-20)},
EPRINT = {http://math.stackexchange.com/q/1444207},
URL = {http://math.stackexchange.com/q/1444207}
}
Wiki status makes no difference either: only the original author is credited. This may be a concern, but one can consider that editors sometimes make substantial contributions to non-wiki posts too, and they are not credited there. Example of a wiki post that was edited by many people, and where the user listed on the site under the question is not the OP:
@MISC {11,
TITLE = {Is $0.999999999... = 1$?},
AUTHOR = {Michael Haren (http://math.stackexchange.com/users/41/michael-haren)},
HOWPUBLISHED = {Mathematics Stack Exchange},
NOTE = {URL:http://math.stackexchange.com/q/11 (version: 2015-09-18)},
EPRINT = {http://math.stackexchange.com/q/11},
URL = {http://math.stackexchange.com/q/11}
}
For deleted users, there is no link to user profile, since they don't have one.
@MISC {389158,
TITLE = {How to calculate $\lim_{n\to\infty}(1+1/n^2)(1+2/n^2)\cdots(1+n/n^2)$?},
AUTHOR = {user17762},
HOWPUBLISHED = {Mathematics Stack Exchange},
NOTE = {URL:http://math.stackexchange.com/q/389158 (version: 2013-05-12)},
EPRINT = {http://math.stackexchange.com/q/389158},
URL = {http://math.stackexchange.com/q/389158}
}
The blue writing inside the "share" dialog is (almost) illegible. Maybe that's whey they moved "cite" away from there...
.cite-link { display: none !important; }$\endgroup$citeanddeletein addition to the box saying the question has been edited make the whole thing too large and it starts wrapping). $\endgroup$