Not really, if you can
t remember the notes you've read you can check their dates
against the last visit date for the top level node in your
history (which you obviously cache before revisiting the page).
Or you could use newest nodes. :-P
Newest nodes doesn't keep track which nodes you have read in any way. Suppose the list of new nodes (new since one last hit the button "I've seen them all") contains nodes A, B, C, all decendents from the same root node. Node B is child of node A, but node A is not a predecessor of node C, but nodes B and C have the same "depth" (that means, they both have exactly the same title if noone changed the titles). Now one visits node A, and node B shows up on the same page as well. So you have read nodes A and B. Now you return to the newest nodes page. Since the links to nodes B and C are different than the link to node A, according to your browser history, you have visited neither B or C. You also remember the date of nodes A and B, and even of the top level node in the thread. Still back on the newest node page, which unvisited link brings you to the unread node, the top or the bottom one?