I am not sure how the software actually works but here are my experiences.
1.) If you read the topic via a selection in the right hand pane labeled "Recent Threads", the bold attribute goes away after being read.
2.) If you read the topic via the "Today's Post" list or via a direct selection from the list in a sub-forum, the topic will not be unbolded until the page is refreshed.
I prefer to use the "Recent Threads" list to see what has changed since the last time I logged on. This method has the advantage of positioning you at the first unread post in the thread. As the list is limited to 16 (?) threads (don't ask me why) I then use the "Today's Post" list. This method positions you at the last post in the thread and you have to find any other posts in the thread that you haven't read.
Carl (n Susan) Youngren
There is more to life than fuel mileage.
2012 Montana 3700RL Big Sky Package towed by a 2015 Ford F350 6.7L PSD 4WD CC LWB