Super short tldr
Don't CV. Either edit, flag or leave a comment for the OP.
Before I answer your question, let me rant a bit :)
Here is the problem with link only questions (LOQ), link only answers (LOA), and like in this case "Here's my blend" questions; inevitably they all go bad.
Indeed this is a problem, which is why this is so heavily discouraged in the first place.
Here are some ideas I have to proactively combat this problem.
I think we should have an outright ban on any images coming from anything other then
i.stack.imgur.com (stack exchange's special image host). 1
I recently when back to a forum that I'm no longer part of, and found all the images are gone. Those were hosted on a site (postimage.org) that at the time said lifetime image hosting. They still say:
You can upload unlimited images per post and you will never have to worry about your images being removed due to inactivity.
Well they are all gone, I don't want our questions (like the linked question) left without important context (and in some cases) the whole question.
i.imgur.com should be considered an outside source and get changed. Yes this would include gifs over 2mb.
I understand that there are many things that simply can not be answered without a blend. So in cases like that we need to be 100% sure that the blend file will stay around. We have Blend-exchange, a site created and maintained by a member of our community. All blends need to be hosted on that site. Pastall is the worst, they guarantee your link will be no good in 5 months, dropbox, google drive, onedrive, any all others should be banned.
There should not be such an emphasize on "the blend." Granted, blends are immensely useful, and help get questions answered quickly. Yet there is a balance, not everything needs a blend. Questions should use text as the number one tool through which information is conveyed.
I believe that in the right hands any question* can be answered without a blend.
As an example from the linked question (dead links underlined in red):
There use to be two images hosted on dropbox; and a blend file on one of those random file sharing sites. As the question is now, it is completely useless.
Now how to deal with posts after the links have gone bad (and to answer your current question). There are a plethora (1, 2, 3, 4) of discussions on this over on the main meta, here I will summarize them and add my own thoughts, specific for BSE.
There are four different cases, and you should take different actions for each.
Dead link only answer.
There should never be a link only answer, and now that the link is dead the answer is worthless.
Flag for for moderator attention, use a custom message and explain that the link is dead. If you have enough rep to vote to delete, then do that too.
Dead link in answer.
When it is a good free standing answer, but has a dead link: Edit the answer and replace the link with a working version. In the case of the old wiki links use the new manual links. (archive.org is always an option.) If you can not find a working link, add a comment for the OP, let them know that their link is dead, and edit out the link - simply remove it completely.
Questions dependent on the dead link(s).
This is the case for the linked question. Add a comment and ask the OP to fix their dead links, also explain where images and blend files should go. Completely edit out the dead links.
If there are no useful answers, flag for moderator attention. Let us know why this should be deleted (dead links). There is hardly ever any reason to close these type of questions, either the answers are still useful or the whole thing can be deleted.
Free standing questions with a dead blend.
Assuming that the link is non essential to understanding the question, which could often be a blend file, as we can not get the original file back, a comment to the OP is the only option. Then completely remove the dead link.
* "Any question" does not include questions that are so unclear, or of poor quality that their meaning can not be deciphered.