Triple-click bug repro

gistfile1.el

(defun repro-filter (fun beg end delete)
  (let ((string (funcall fun beg end delete)))
    (with-temp-buffer
      (insert string)
      string)))

(with-current-buffer (get-buffer-create "*Bug*")
  (set (make-local-variable 'filter-buffer-substring-functions)
       '(repro-filter))
  (insert "Hello, World!\n")
  (pop-to-buffer (current-buffer)))