"Sort by popularity" and/or relevance
Going through a feed you haven't read for a few days can be painful, as hundreds or even thousands of posts may have piled up in the meantime.
Today, your options are going through everything or just marking it read and restarting.
I want a middle way, where you can sort the feed by popularity (# of starred, # of people who've clicked through, I'm sure you have a lot of metrics that can be combined to form 'popularity' ).
That way, you'll hopefully get more of the best posts you've missed in easy reach, and when you feel you've 'reached the cruft' you can just mark all as read.
A "Sort by relevance" taking into account mainly your activities would be even better, but may be harder to implement(?).