When someone links to a question, at some time in the future the question that has been linked to may get moved to a more appropriate site. I have come across this several times while finding answers on the SO sites. When this happens, all you get is the standard SO 404 error message (case in point, the link in the comment from this answer). It would be nice if the SO engine could recognize that the question once existed but has been moved and automatically redirect to the actual question.
So when a post gets migrated, the engine would full-text-search it's entire database looking for that URL fragment (up to the title, which is unnecessary)?
I like the idea; it'd be nice to keep everything clean. I just can't imagine that this would be good for performance, though.
If the question is moved, then there will be a stub with a link to the migrated question.
If the question is deleted (as is the case here) you'll get the 404 error, unless you're a 10k+ user.