I’d assume this is the result of someone locking and unlisting a fresh thread, but this indicator is extremely annoying. I am unable to access the thread that is listed here, thus I cannot dismiss the notification by simply opening the thread and reading its contents. It’s been like this for some hours.
Have you attempted to go into your category settings (go to preferences on your userpage, go to notifications, and then click on categories) where you can mute the category, save, and then unmute?
It may simply be something that has to be muted and unmuted for the indicator to disappear.
The new thread notification is gone and I am happy. I guess waiting it out worked and I should’ve waited some more time before asking for help about it.