--- a/.emacs-my	Fri Apr 05 00:21:08 2013 +0300
+++ b/.emacs-my	Mon Apr 08 01:00:32 2013 +0300
@@ -1672,6 +1672,17 @@
      (add-hook 'message-sent-hook 'gnus-score-followup-thread)
      ))
 
+(defun my-gnus-summary-kill-same-subject (&optional unmark)
+  "Add negative scores for all articles with same subject."
+  (interactive "P")
+  (when (or (not (integerp unmark)) (< 0 unmark))
+    (gnus-summary-score-entry
+     "subject" (gnus-simplify-subject-fuzzy (gnus-summary-article-subject))
+     's (- gnus-score-interactive-default-score) (current-time-string)))
+  (gnus-summary-kill-same-subject unmark))
+(eval-after-load 'gnus-summary
+  '(define-key gnus-summary-mode-map (kbd "C-k") #'my-gnus-summary-kill-same-subject))
+
 (defun my-gnus-thread-score-function (&rest scores)
   "If any followup have positive score assign greater available
 score to thread, else assign lesser available score."