I've seen a few people talk about how they are bookmarking /recent/all instead of /recent/unread. I wasn't sure why they were working this way, but realized they might not realize how /unread works.
/unread lists all Posts and Questions on MaplePrimes that you have not viewed. Once you click on one of those items, it no longer appears on the list. However, if the item is updated or a comment or answer is added to the item, it will re-appear in the /unread list. This means that by checking /unread, you will see everything that is posted to MaplePrimes, even if it posted after you last viewed that thread.
I believe the confusion was that items don't re-appear in the /unread when replies are posted, so people were viewing /all so they could see everything. I hope this clears things up.