Are you thinking of something like Stack Overflow’s reputation system? See https://stackoverflow.com/help/whats-reputation for a basic overview. See https://stackoverflow.com/help/privileges for some examples of privileges unlocked by hitting a particular reputation level.

That system is better optimized for reputation than the threaded discussions that we participate in here, but it has its own problems. However, we could at minimum learn from the things that it does right:

• You need site (or community) staff, who are not constrained by reputation limits, to police the system
• Upvoting is disabled until you have at least a little reputation
• Downvoting is disabled until you have a decent amount of reputation and costs you reputation
• Upvotes grant more reputation than downvotes take away
• Voting fraud is a bannable offense and there are methods in place to detect it
• The system is designed to discourage reuse of content
• Not all activities can be upvoted or downvoted. For example, commenting on SO requires a minimum amount of reputation, but unless they’re reported as spam, offensive, fraudulent, etc. (which also requires a minimum reputation), they don’t impact your reputation, even if upvoted.

If you wanted to have upvoted and downvoted discourse, you could also allow people to comment on a given piece of discourse without their comment itself being part of the discourse. For example, someone might just want to say “I’m lost, can someone explain this to me?” “Nice hat,” “Where did you get that?” or something entirely off topic that they thought about in response to a topic.

You could also limit the total amount of reputation a person can bestow upon another person, and maybe increase that limit as their reputation increases. Alternatively or additionally, you could enable high rep users to grant more reputation with their upvotes (either every time or occasionally) or to transfer a portion of their rep to a user who made a comment they really liked. It makes sense that Joe Schmo endorsing me doesn’t mean much, but King Joe’s endorsement is a much bigger deal.

Reputation also makes sense to be topic specific. I could be an expert on software development but be completely misinformed about hedgehogs, but think that I’m an expert. If I have a high reputation from software development discussions, it would be misleading when I start telling someone about hedgehogs diets.

Yet another thing to consider, especially if you’re federating, is server-specific reputations with overlapping topics. Assuming you allow users to say “Don’t show this / any of my content to at all,” (e.g., if you know something is against the rules over there or is likely to be downvoted, but in your community it’s generally upvoted) there isn’t much reason to not allow a discussion to appear in two or more servers. Then users could accrue reputation on that topic from users of both servers. The staff, and later, high reputation users of one server could handle moderation of topics differently than the moderators of another, by design. This could solve disagreements about moderation style, voting etiquette, etc., by giving users alternatives to choose from.