What is considered proper attribution for a deleted Stack Exchange post?

Question

When a creator posts content to any Stack Exchange site, they grant Stack Exchange a Creative Commons Attribute Share-Alike license to use (and display and share) the content. This is irrevocable - even if you choose to delete your post, or a moderator deletes your post, Stack Exchange still has a license to use it.

Stack Exchange has chosen to allow users with 10k reputation, site moderators, and some staff to view deleted posts. That means that this class of user can, potentially, receive a CC BY-SA license to all content ever posted on a given site and use it, under the CC BY-SA license.

Creative Commons provides the following rules for providing attribution:

If supplied, you must provide the name of the creator and attribution parties, a copyright notice, a license notice, a disclaimer notice, and a link to the material. CC licenses prior to Version 4.0 also require you to provide the title of the material if supplied, and may have other slight differences.

One of the requirements is "a link to the material". Since the content has been deleted, it is no longer accessible to people who do not fit the criteria who can view it. However, the post still does have a URL (should it ever become undeleted, for example).

Would linking to a deleted post (while providing the other required information) be considered proper attribution under the Creative Commons rules? If not, what would proper attribution to a deleted Stack Exchange post look like?

Note that this does not consider the ethics of using a deleted post. I have received the post and have the right to use it. For a cultural/ethical discussion, see this post on Meta Stack Exchange.

Answer 1

In 4(c) of CC BY-SA 3.0 it is defined how attribution has to be provided. For the work’s URL, it says:

[…] (iii) to the extent reasonably practicable, the URI, if any, that Licensor specifies to be associated with the Work, unless such URI does not refer to the copyright notice or licensing information for the Work; […]

So

• if a work’s page no longer exists, or
• if the page is about something different now, or
• if the page does not (or never did) contain the information that the work is licensed under CC BY-SA 3.0,

you don’t have to provide the URL in your attribution.

But you may still do so, and I think it can be beneficial: it allows others to find the work in Web archives; maybe the page comes back online again; it can be relevant to know under which domain the work was originally hosted; etc. If you decide to provide the URL, it might be a good idea to add a note that it no longer works (and, perhaps, to use the nofollow link type, in case of HTML).

However, I think that this does not apply to "deleted" posts from Stack Exchange sites. These pages still contain the relevant information (they are still about the work, and they still contain the licensing information), it’s just that they are (currently) not accessible to unregistered and many registered visitors.

These posts are still "available to the public" (from CC BY-SA 3.0’s definition of Distribute), similar to a book that’s for sale, a performance that requires an admission ticket, a Web video that can only be streamed from a specific country, or a newspaper article behind a paywall. In the case of Stack Exchange, an account with 10k reputation or moderator privileges is required. If at some point only Stack Exchange employees would be able to access "deleted" posts, then I’d consider these to no longer be available to the public.