diff --git a/src/applications/herald/field/HeraldField.php b/src/applications/herald/field/HeraldField.php
--- a/src/applications/herald/field/HeraldField.php
+++ b/src/applications/herald/field/HeraldField.php
@@ -177,25 +177,26 @@
   }
 
   public function getPHIDsAffectedByCondition(HeraldCondition $condition) {
-    $phids = array();
+    try {
+      $standard_type = $this->getHeraldFieldStandardType();
+    } catch (PhutilMethodNotImplementedException $ex) {
+      $standard_type = null;
+    }
 
-    $standard_type = $this->getHeraldFieldStandardType();
     switch ($standard_type) {
       case self::STANDARD_PHID:
       case self::STANDARD_PHID_NULLABLE:
-        $phid = $condition->getValue();
-        if ($phid) {
-          $phids[] = $phid;
-        }
-        break;
       case self::STANDARD_PHID_LIST:
-        foreach ($condition->getValue() as $phid) {
-          $phids[] = $phid;
+        $phids = $condition->getValue();
+
+        if (!is_array($phids)) {
+          $phids = array();
         }
-        break;
+
+        return $phids;
     }
 
-    return $phids;
+    return array();
   }
 
   final public function setAdapter(HeraldAdapter $adapter) {
diff --git a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
--- a/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
+++ b/src/applications/transactions/storage/PhabricatorApplicationTransaction.php
@@ -775,6 +775,13 @@
       case PhabricatorTransactions::TYPE_TOKEN:
       case PhabricatorTransactions::TYPE_MFA:
         return true;
+      case PhabricatorTransactions::TYPE_SUBSCRIBERS:
+        // See T8952. When an application (usually Herald) modifies
+        // subscribers, this tends to be very uninteresting.
+        if ($this->isApplicationAuthor()) {
+          return true;
+        }
+        break;
       case PhabricatorTransactions::TYPE_EDGE:
         $edge_type = $this->getMetadataValue('edge:type');
         switch ($edge_type) {
@@ -1387,12 +1394,6 @@
           return 25;
         }
 
-        if ($this->isApplicationAuthor()) {
-          // When applications (most often: Herald) change subscriptions it
-          // is very uninteresting.
-          return 1;
-        }
-
         // In other cases, subscriptions are more interesting than comments
         // (which are shown anyway) but less interesting than any other type of
         // transaction.