When scrolling through Lemmy, I often will see the same posts from the previous page - usually as the first links on the current page I’m on.
Lazy programming.
The naive way to do pagination is to say show me items x through y. But obviously if the back end is dynamic, x through y could change. So the better way to program pagination is to say show me items above item n, too item n plus x. Then you can have dynamic pagination based on the last comment, you saw.
Another way to do this is have your session look at a static snapshot of the dynamic database, until you refresh the page or go back to the top. This is possible with a lot of different databases, kind of like how ZFS can give you snapshots of root at any time.
FartsWithAnAccent@lemmy.world 1 year ago
Just speculating but, as new posts are made, it pushes the other posts up some, which can make them show up again when you hit next (or hit the infinite scrolling reload point).