Here's the new algorithm in a nutshell: Posts are listed in your feed according to their score. The score is 1 by default. It falls off to 0 with time. Every time it is shared (or badged) a bit is added to the score, and then it is fed back into the decay equation. So even if a post is really old, a single share should bump it into people's feeds. This new system should be integrated into the site code in the next couple days. We'll see how it works. I'm very proficient at math, but not at computer code, so it could be a train wreck.