Maybe EarlG is reading this thread and can comment, though work on twitter/bluesky matters is no doubt more urgent.

which tells you there are new unread messages. It is like with your email folders, "mark all read."

Go to any forum and you'll see the little icons to the left of the post titles. Or go into any thread, and you'll see little icons to the left of each reply. Any time a new OP or reply is posted, it gets a yellow icon.

However, if you click the "Mark All" button, those icons all change from yellow to white. Then, as new OPs or replies are posted, they will have a yellow icon. In this way -- if you use the Mark All button regularly -- you can see at a glance which posts are new and which are not.

The traditional way to use this is to simply click "Mark All" at the end of your DU browsing session. Then, the next time you come back to DU, new items will be yellow, whereas items which were there the last time you read DU will still be white.

If you prefer to mark forums individually, each forum has its own "Mark" button at the top which only changes icons in that forum from yellow to white. If you use "Mark All" on the Latest/Greatest/Latest Videos pages, it changes all the icons on the site from yellow to white.