The debian alternative "editor" should probably be consulted when determining the
"sensible-editor".  It would make sense to attempt this after $EDITOR, as $EDITOR is user
 configured while sensible-editor is system configured.

I would also like to see "sensible-editor" attempt some X based editors in the event that
display is set (as sensible-browser does).

I see xemacs gets entered as an alternative for "editor".
There should be an x-editor alternative for editors such as xemacs, gedit, and knotepad.  But,
that is probably a bug report for another package.

"editor" is attempted if $EDITOR is unset; is there value in trying
"editor" if $EDITOR is set and fails?

We need the alternative you mention in order to do this.

Yes, you would file bugs against those editors.

Hi there!

in the absence of environment variables or ~/.selected_editor,
sensible-editor appears to choose from:

 * nano
 * nano-tiny
 * vi

It does not try /usr/bin/editor.  It should try /usr/bin/editor before
trying any of the above (while still allowing the environment
variables and ~/.selected_editor to override the system alternative).