What exactly would be the advantages of this for a user? (I can think of lots disadvantages.)
My suspicion is anyone deleting a directory either wants the information within it destroyed or doesn't want to delete the directory after all.
Certainly, more "fuzzy" relations and storage could have their uses - like a downloaded music directory where the least listened songs go away automatically when you need more space. But you would not want to make your entire file system "fuzzy" in the sense that you don't know what's gone and what isn't.
The trashcan/recycle-bin is a great interface for undoing what you thought was the deletion of a file. This, not so much.
Then it seems you haven't used symlinks or hardlinks very much. I do it to organize my code, because it's useful to have more than one way to get to folder X (I have things organized by language, then they all go to a master code folder which reorganizes them in versioned/not, mine/downloaded, etc). It makes finding what I'm looking for very easy, it's easy to script changes / restrict searches / update everything in one go.
But using symlinks means I can't reorganize without great cost, because they don't follow movements around. It also means some of my folders look like shortcuts while some don't, stepping into one causes my path to change wildly (no backing up, usually), and in order to protect my data I have to make sure I never delete (or move) the originals, only the symlinks.
Or say you want to organize your images in two photo applications at the same time - hardlinks mean each can have full control over where they place their file, without interrupting the other, and without duplicating what could be an enormous amount of data.
OSX attempts to solve this with Aliases - essentially, "smart" symlinks that follow changes. If you alias a file and then move the original, the alias will still work. The downside is that essentially no command-line tools handle them in any way, because they're decidedly non-standard. Being able to hardlink folders would allow filesystem organizations not possible before, with safety, tool-compatibility, and efficiency.
My suspicion is anyone deleting a directory either wants the information within it destroyed or doesn't want to delete the directory after all.
Certainly, more "fuzzy" relations and storage could have their uses - like a downloaded music directory where the least listened songs go away automatically when you need more space. But you would not want to make your entire file system "fuzzy" in the sense that you don't know what's gone and what isn't.
The trashcan/recycle-bin is a great interface for undoing what you thought was the deletion of a file. This, not so much.