Pulling the data when a user requests a post/comment (with a cooldown/cache for popular posts) isn’t any more or less scalable than feddit.de pushing the same data whether it’s been requested or not. If anything, I’d think pushing data when it’s not necessarily needed would be less scalable.
But if it has to be a push model, why doesn’t feddit.dk push the votes it knows about along with the rest of the data?