diff --git a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
--- a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
+++ b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
@@ -780,6 +780,33 @@
     switch ($this->getTransactionType()) {
       case PhabricatorTransactions::TYPE_COMMENT:
         return 0.5;
+      case PhabricatorTransactions::TYPE_SUBSCRIBERS:
+        $old = $this->getOldValue();
+        $new = $this->getNewValue();
+
+        $add = array_diff($old, $new);
+        $rem = array_diff($new, $old);
+
+        // If this action is the actor subscribing or unsubscribing themselves,
+        // it is less interesting. In particular, if someone makes a comment and
+        // also implicitly subscribes themselves, we should treat the
+        // transaction group as "comment", not "subscribe". In this specific
+        // case (one affected user, and that affected user it the actor),
+        // decrease the action strength.
+
+        if ((count($add) + count($rem)) != 1) {
+          // Not exactly one CC change.
+          break;
+        }
+
+        $affected_phid = head(array_merge($add, $rem));
+        if ($affected_phid != $this->getAuthorPHID()) {
+          // Affected user is someone else.
+          break;
+        }
+
+        // Make this weaker than TYPE_COMMENT.
+        return 0.25;
     }
     return 1.0;
   }