There is already a total count of up- and downvotes, but please never add karma to Lemmy. We don't want to deal with karma farmers and minimal karma requirements to post. I don't care about the moderation issues because karma brought more harm than good. Please never add that bloody dreadful thing to Lemmy. I already saw a bunch of people supporting adding karma to Lemmy, which will turn Lemmy into a cheap Reddit clone and karma-farming hell. Please, never add karma to Lemmy. I beg you. No more karma hell.
The votes were not equal to karma. Karma wasn't just subtracting downvotes from upvotes. They made a function that not every up- and downvote changed karma. It was a weird mathematical function. Karma was also used to limit you from posting on some subreddits. That's the reason why I heavily dislike karma.
Karma was originally visible raw upvote / downvote tally. Reddit just obscured the upvote and downvote numbers to discourage manipulation for karma.
Limiting participation based on karma didn’t happen for a long time. By the time some huge subreddits took that step, it (or some other gatekeeping) was necessary to filter a lot of malicious users.
Kiiinda… You were limited on the amount of karma a single post or comment could raise or lower your accounts score. It’s not a complex algorithm by any means, just slightly convoluted.
It prevent things like mass-downvoting from counting much towards karma AFAIK, but that's more/less the idea of karma. The exact way it was calculated had nothing to do with people trying to game it. Minimums to post in communities did mean spamming elsewhere just to be able to post where you wanted though and the economic worth of "trustworthy accounts" made karma a karma an issue. Upvotes - downvotes still functions for the latter purpose. If people decide the fediverse is worth scamming, then farming will be a thing. Right now, its a fairly small niche space with an average user who is more internet-savvy than most mainstream social media users, so its probably not worth the effort of trying to scam here yet...