Remove ~/Desktop folder
After a new installation, there's a folder called Desktop in your Home folder.
It's marked with a special icon, and it cannot be deleted in the usual way, but otherwise it doesn't behave differently from any other folder.
Users may believe that putting files into this folder will make them appear on the desktop background, but this is not the case.
There is no ~/Desktop folder.
Benefits of the solution
Users will not be confused by this odd folder that looks like it should behave specially, but actually doesn't.
Any future implementation of icons on the desktop would need to create its own Desktop folder.
XDG_DESKTOP_DIR (as defined in ~/.config/user-dirs.dirs) would need to change:
If we change this to "$HOME", that might lead to some minor confusion: the use-cases for a Desktop folder (quick access to urgent or short-lived items) are not exactly the same as the use-cases for the Home folder (quick access to important and long-lived items).
We could instead change this to "$HOME/Downloads", but this also isn't perfect. Some applications may assume that putting a file in the Desktop folder will make it virtually impossible for the user to lose, whereas this isn't quite true of the Downloads folder.
On balance I think XDG_DESKTOP_DIR="$HOME" is reasonable.