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.
Anybody want to post what the mod log looks like at this point?