@harris for (3), why exclude higher-ranked things you haven't seen yet?
@harris since you're proposal is in strict priority order posts would get less and less interesting to you as you scrolled down, so you might not need a strict limit to tell you that it was time to be done, it might just get boring?
(Facebook, Twitter, etc don't use strict priority order for this reason, pretty sure)
@jefftk Good point. I suppose it could append those to the list, though at some point if I was regularly not reading everything there would be a years long tail of very old posts. Maybe some sort of limit, because I like the idea of it eventually telling me I'm caught up so I can close it and do other stuff.