Add a comment.

Signal/src/ViewControllers/ConversationView/ConversationViewController.m

@@ -2950,6 +2950,8 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
     if (shouldAnimateUpdates) {
         [self.collectionView performBatchUpdates:batchUpdates completion:batchUpdatesCompletion];
     } else {
+        // We want these animations to be as short as possible, but `performBatchUpdates`
+        // will SIGABORT in some cases if the animation duration is zero.
         [CATransaction begin];
         [CATransaction setAnimationDuration:0.05f];
         [self.collectionView performBatchUpdates:batchUpdates completion:batchUpdatesCompletion];