Wait, my intented question was, `do those backup files have the executable permission bits set'? Not `do they hold valid input for interpreter/CPU'.

In Slackware's startup scripts, there's a good bunch of

  if [ -x SOME_FILE ]; then    # if the file is executable, run it
    ./SOME_FILE start
  fi

which makes it trivial to enable/disable various services by simply chmod +x SOME_FILE / chmod -x SOME_FILE. If EMACS' backup files were marked as not executable by the editor, that would be `case closed' for me, no need to pay extra attention to characters in file names.