There’s some misinformation floating around regarding Lemmy not having a karma system. While many have discovered otherwise, this is for those who may not have.
While it’s not exposed in the Lemmy default user interface, Lemmy does have a fully functional karma system and it is visible in third party clients such as WefWef and Memmy.
Do with that what you will.
It’s right in the API: https://join-lemmy.org/api/interfaces/PersonAggregates.html
Returns: comment_count, comment_score, id, person_id, post_count, post_score