Just because it can be done client side doesn’t mean it should be done client side. ¯_(ツ)_/¯ In this case, other APIs, like Reddit automatically filter your own posts and comments from upvoted and downvoted lists, because it doesn’t make sense to show that information. So in this case, I think it’s best to open an issue with Lemmy. Although I doubt it, if they don’t want to implement it on the backend, then it can be handled client side.