How should dead links in questions and answers be handled when found - should they be marked as such, removed, or similar?
For example, in this answer, the links to pages on the GitHub site now return 404 File Not Found.
It would seem sensible to do something with them so that people know that following them is pointless.
It depends on what the link is.
In the example you pointed out, it was easy to find the up-to-date link to the standard, so I edited the answer to use the correct link.
In general, there will sometimes be a new link with the same information, or - as the other answer points out - you might be able to find an archive link. You can edit (or suggest an edit), or add a comment to point out the new link.
In this case, since the relevant text from the link was included in the answer, it's not critical to update the link, but it's worth doing when you notice one.
For dead link it's a long process, but if you find one you can edit to add a web.archive's link.
Like in your answer I found that one; https://web.archive.org/web/20190115142142/https://http2.github.io/http2-spec/ that could replace it.
In the answer example it's good as the answerer put time to copy/paste the correct section, in case it's no longer retrievable, but in case there is no information pasted I would had recommended too to paste the information to be sure we don't loose the information if the web archive don't have the information.
