Yup. I agree with the GP’s general premise, but I wouldn’t make high-karma posters have their comments appear higher. Instead, I’d weight their up/downvotes on other people’s comments proportional to their karma, but only in subreddits where they accrued karma. Thus, someone who accrued 10000 karma in history subreddits might get e.g. 10x the voting power in history subreddits. However, if they only had 10 karma in science subreddits, their votes would not be worth a lot there.

Of course, this is not perfect (what if someone posts about history in a science subreddit, or vice versa), but it’s a start. AFAIK no platform has tried weighted voting yet.