a button like that will be good to program. i looked to see how it can be done. usually the links a page will be shown differently if they were visited. we cant get the visited links info from js (https://stackoverflow.com/a/7291538).
the list is updated and sometimes it will have less than 30 or more than 70 links. 30 links can be shown in a single page. when there are more than 70, a btn like above will be useful. Will definitely add this btn if the site gets regular visits.
I think this is simple enough to be useful. Banned/Flagged posts will be striked out. 8hrs seem reasonable time frame. It is only for people who read HN mostly and contribute to HN rarely.