How Do I Make My Thread Title Bold?

Chances are, a 'bold title' is not what you think it is. Nor can you just make it bold; in fact, the only reason your thread title would not be bold is because you've already clicked on the thread as a logged-in user*. 

*This functionality does not apply to logged-out or incognito users.

Once you click on a thread (as a logged-in user), the forum marks it as 'read' on your account, changing the thread title back to a normal typeface, i.e. it is no longer bold, as shown in the example below:

Title before clicking on a thread:

Title after clicking on a thread:

You may also notice that some titles in the Main Forum List appear in bold: in short, any sub-forums with new threads you've yet to visit, will appear in bold (when you're visiting as a logged-in user).

To mark the sub-forum as read, you must be logged in and visit just one of the unread THREADS in that forum. Please note that you need to actually visit one of the new threads, not just the forum, for it to identify that you've read the new THREADS in that sub-forum. That forum will then no longer appear as bold but as a normal typeface.

Newbie guide article: https://www.blackhatworld.com/seo/how-do-i-make-my-thread-title-bold.1291023/