Just wanted to bump this with what (I think?) is a compelling argument for a “Mark as Read” feature within categories.
I have just begun watching an active category with a long history, and am avidly reading every new topic and post in it.
But on the left nav, the category name always has its blue dot next to it, because of the many old topics I haven’t looked at, and don’t have the time to go through.
This leaves me no way to tell “at a glance” whether there is new content in this category.