CR: Clean up comments, use property setter instead of ivar

// FREEBIE

SignalServiceKit/src/Devices/OWSLinkedDeviceReadReceipt.m

@@ -44,9 +44,8 @@ NS_ASSUME_NONNULL_BEGIN
 
     // For legacy objects, before we were tracking read time, use the original messages "sent" timestamp
     // as the local read time. This will always be at least a little bit earlier than the message was
-    // actually read, but it's the safer assumption. At worst we'll delete the message from this device
-    // earlier than the user expects, but this shouldn't be terrible because we know they've read the
-    // message on the other device. Keep in mind this *only* affects "early" read receipts.
+    // actually read, which isn't ideal, but safer than persisting a disappearing message too long, especially
+    // since we know they read it on their linked desktop.
     if (_readTimestamp == 0) {
         _readTimestamp = _messageIdTimestamp;
     }

SignalServiceKit/src/Messages/OWSDisappearingMessagesJob.m

@@ -72,11 +72,11 @@ void AssertIsOnDisappearingMessagesQueue()
     NSTimeInterval kFallBackTimerInterval = 5 * kMinuteInterval;
     [AppReadiness runNowOrWhenAppIsReady:^{
         if (CurrentAppContext().isMainApp) {
-            self->_fallbackTimer = [NSTimer weakScheduledTimerWithTimeInterval:kFallBackTimerInterval
-                                                                        target:self
-                                                                      selector:@selector(fallbackTimerDidFire)
-                                                                      userInfo:nil
-                                                                       repeats:YES];
+            self.fallbackTimer = [NSTimer weakScheduledTimerWithTimeInterval:kFallBackTimerInterval
+                                                                      target:self
+                                                                    selector:@selector(fallbackTimerDidFire)
+                                                                    userInfo:nil
+                                                                     repeats:YES];
         }
     }];
 

SignalServiceKit/src/Messages/OWSReadReceiptManager.m

@@ -464,7 +464,7 @@ NSString *const OWSReadReceiptManagerAreReadReceiptsEnabled = @"areReadReceiptsE
         }
 
         if (messageIdTimestamp == 0) {
-            OWSProdLogAndFail(@"%@ in %s messageIdTimstamp was unexpectedly 0", self.logTag, __PRETTY_FUNCTION__);
+            OWSProdLogAndFail(@"%@ in %s messageIdTimestamp was unexpectedly 0", self.logTag, __PRETTY_FUNCTION__);
             continue;
         }