I don't know if this is an issue with my PC or not. Many times threads with new replies do not turn the balloon red. And then there's times when the notification balloon is red and there haven't been any new replies posted since I last read all current replies. This is been going on for maybe a year, not really sure but it has been a long time so it's not something that's just popped up.

Browsers I use - Chrome & Firefox, but primarily Chrome. Both exhibit the same symptoms and are currently updated.
Windows 10