Sorry guys, nothing mentioned here helped.
Still the thread shows in unread...
If you still haven't fixed the issue, you should check to see if you actually subscribed to the topic and if you did then you would be getting notifications about new replies and to unsubscribe, toggle to your profile then notifications and email there if you find the topic check the box and hit unsubscribe.
If this doesn't fix it go to the board and page you have that particular post , click the checkbox for the post and press mark as read on the top right corner. Then also open the thread and press
unwatch on the top right corner.
Currently I am unsubbed to this topic.
I see "watch" and "notify".
In Watchlist editor I don't see this topic, it isn't there.
I've done all of these and now on unread topics page it appeared. It shouldn't.
I have no email subscription to receive emails about posting in threads, so I cannot click there anything.