diff --git a/src/applications/calendar/controller/PhabricatorCalendarEventEditController.php b/src/applications/calendar/controller/PhabricatorCalendarEventEditController.php
index 3211d8052b..928526f33f 100644
--- a/src/applications/calendar/controller/PhabricatorCalendarEventEditController.php
+++ b/src/applications/calendar/controller/PhabricatorCalendarEventEditController.php
@@ -34,7 +34,17 @@ final class PhabricatorCalendarEventEditController
             ->addCancelButton($cancel_uri);
         }
       } else if ($event->getIsRecurring()) {
-        $mode = $request->getStr('mode');
+
+        // If the user submits a comment or makes an edit via comment actions,
+        // always target only the current event. It doesn't make sense to add
+        // comments to every instance of an event, and the other actions don't
+        // make much sense to apply to all instances either.
+        if ($engine->isCommentAction()) {
+          $mode = PhabricatorCalendarEventEditEngine::MODE_THIS;
+        } else {
+          $mode = $request->getStr('mode');
+        }
+
         if (!$mode) {
           $form = id(new AphrontFormView())
             ->setViewer($viewer)
@@ -60,7 +70,6 @@ final class PhabricatorCalendarEventEditController
             ->addSubmitButton(pht('Continue'))
             ->addCancelButton($cancel_uri)
             ->setDisableWorkflowOnSubmit(true);
-
         }
 
         $engine
diff --git a/src/applications/calendar/editor/PhabricatorCalendarEventEditEngine.php b/src/applications/calendar/editor/PhabricatorCalendarEventEditEngine.php
index f877bd9d13..c56cd7febb 100644
--- a/src/applications/calendar/editor/PhabricatorCalendarEventEditEngine.php
+++ b/src/applications/calendar/editor/PhabricatorCalendarEventEditEngine.php
@@ -295,7 +295,7 @@ final class PhabricatorCalendarEventEditEngine
 
   protected function willApplyTransactions($object, array $xactions) {
     $viewer = $this->getViewer();
-    $this->rawTransactions = $xactions;
+    $this->rawTransactions = $this->cloneTransactions($xactions);
 
     $is_parent = $object->isParentEvent();
     $is_child = $object->isChildEvent();
@@ -304,6 +304,30 @@ final class PhabricatorCalendarEventEditEngine
     $must_fork = ($is_child && $is_future) ||
                  ($is_parent && !$is_future);
 
+    if ($is_parent && !$is_future) {
+      // We don't necessarily need to fork if whatever we're editing is not
+      // inherited by children. For example, we can add a comment to the parent
+      // event without needing to fork. Test all the stuff we're doing and see
+      // if anything is actually inherited.
+
+      $inherited_edit = false;
+      foreach ($xactions as $xaction) {
+        $modular_type = $xaction->getTransactionImplementation();
+        if ($modular_type instanceof PhabricatorCalendarEventTransactionType) {
+          $inherited_edit = $modular_type->isInheritedEdit();
+          if ($inherited_edit) {
+            break;
+          }
+        }
+      }
+
+      // Nothing the user is trying to do requires us to fork, so we can just
+      // apply the changes normally.
+      if (!$inherited_edit) {
+        $must_fork = false;
+      }
+    }
+
     if ($must_fork) {
       $fork_target = $object->loadForkTarget($viewer);
       if ($fork_target) {
@@ -340,7 +364,7 @@ final class PhabricatorCalendarEventEditEngine
     }
 
     foreach ($targets as $target) {
-      $apply = clone $this->rawTransactions;
+      $apply = $this->cloneTransactions($this->rawTransactions);
       $this->applyTransactions($target, $apply);
     }
   }
@@ -366,4 +390,12 @@ final class PhabricatorCalendarEventEditEngine
     }
   }
 
+  private function cloneTransactions(array $xactions) {
+    $result = array();
+    foreach ($xactions as $xaction) {
+      $result[] = clone $xaction;
+    }
+    return $result;
+  }
+
 }
diff --git a/src/applications/calendar/xaction/PhabricatorCalendarEventReplyTransaction.php b/src/applications/calendar/xaction/PhabricatorCalendarEventReplyTransaction.php
index e2ad9ea4be..2aad3d2bb2 100644
--- a/src/applications/calendar/xaction/PhabricatorCalendarEventReplyTransaction.php
+++ b/src/applications/calendar/xaction/PhabricatorCalendarEventReplyTransaction.php
@@ -8,6 +8,10 @@ abstract class PhabricatorCalendarEventReplyTransaction
     return $object->getUserInviteStatus($actor_phid);
   }
 
+  public function isInheritedEdit() {
+    return false;
+  }
+
   public function applyExternalEffects($object, $value) {
     $acting_phid = $this->getActingAsPHID();
 
diff --git a/src/applications/calendar/xaction/PhabricatorCalendarEventTransactionType.php b/src/applications/calendar/xaction/PhabricatorCalendarEventTransactionType.php
index 53c00969e9..bcb1e13c21 100644
--- a/src/applications/calendar/xaction/PhabricatorCalendarEventTransactionType.php
+++ b/src/applications/calendar/xaction/PhabricatorCalendarEventTransactionType.php
@@ -1,4 +1,10 @@
 <?php
 
 abstract class PhabricatorCalendarEventTransactionType
-  extends PhabricatorModularTransactionType {}
+  extends PhabricatorModularTransactionType {
+
+  public function isInheritedEdit() {
+    return true;
+  }
+
+}
diff --git a/src/applications/transactions/editengine/PhabricatorEditEngine.php b/src/applications/transactions/editengine/PhabricatorEditEngine.php
index f22c113f8e..feb710295f 100644
--- a/src/applications/transactions/editengine/PhabricatorEditEngine.php
+++ b/src/applications/transactions/editengine/PhabricatorEditEngine.php
@@ -780,7 +780,7 @@ abstract class PhabricatorEditEngine
     $controller = $this->getController();
     $request = $controller->getRequest();
 
-    $action = $request->getURIData('editAction');
+    $action = $this->getEditAction();
 
     $capabilities = array();
     $use_default = false;
@@ -2098,6 +2098,17 @@ abstract class PhabricatorEditEngine
       PhabricatorPolicyCapability::CAN_EDIT);
   }
 
+  public function isCommentAction() {
+    return ($this->getEditAction() == 'comment');
+  }
+
+  public function getEditAction() {
+    $controller = $this->getController();
+    $request = $controller->getRequest();
+    return $request->getURIData('editAction');
+  }
+
+
 /* -(  Form Pages  )--------------------------------------------------------- */