I’ve seen it as well. A part of it is because posts get down voted, so when you scroll down it gets displayed twice since it moved in the ranking in between loading. This also means if a post gets up voted, you can easily miss it. It’s only an issue with posts that have few votes usually, so not a huge deal.

But I’ve also seen where the same few posts just repeat twice for seemingly no reason. I’m not really sure how the data gets retrieved. With other systems I’ve seen a “session” associated with a cursor. That cursor moves through the data, maintaining the order. That way it doesn’t matter that stuff changes in between client data retrieval. Lemmy doesn’t seem to work like that, simply querying the database with filters. That isn’t the best honestly.