Frankly I disagree with the notion this is going to create any sort of cultural impact. At higher levels, there is no room to curate players based on behavior. You basically play with the dudes you get and barring absurd toxicity that gets you banned, that's what it comes down to. Then the people slightly below the top level that regularly watch streams are going to see the high level players disregard the karma system or consider it a joke and mimic the exact same behavior.
Continue on down the daisy chain and there's no real reason for some culture to manifest where anyone cares about the impact of it. I sure wouldn't look at it. If I want to curate a player, I look at their replay vault for what kind of games they play. As far as I know, this is how everyone else does it other than some teamgame dudes which keep their Bad Attitude (tm) list while ironically being people that get called out for their own Bad Attitudes. The major users of such a system are probably going to be these half a dozen guys that keep their death excel sheets for their 6v6 games because someone said they played like garbage and then a passive aggressive war ensued.
If there's no negative "warning this guy is mad toxic don't join this game" then what's the point of the system for new players. They join this 600 with 10,000 games that's toxic, are unaware that karma is a thing, and go play the game. Then a dozen games down the line when they complain about the toxicity of FAF they are told that this karma system is a thing and then get upset it doesn't do anything so what's the point in caring about it?
As far as I know karma systems in other games are deeply integrated into the matchmaking service of games. You get terrible karma, you get put in lobbies with others with terrible karma. Problem is FAF is self selecting so it's entirely up to the community to proactively create a culture around caring about karma rating, and we aren't big enough at higher levels of play to ever care about it. Best case scenario you have some "elo hell" where karma matters at <1000 or whatever rating and then suddenly no one ever gives a single care in the world about it.
Another thing I just recalled, I really enjoy seeing Gyle casts where a guy quits because the game is over and then I go into the comment section and see a bunch of dudes mad because a guy didn't play a game to conclusion and consider it "poor sportsmanship in FAF." If we allow "experienced players" to go and rate players, I'm assuming it's possible to adjust karma without being in a game. In which case, I eagerly await the Gyle Audience Good Behavior (tm) witchhunts.
All in all, if the entrenched FAF playerbase is so toxic it drives away players, I fail to see how creating a system which in turn allows this toxic playerbase to go and rate players is the solution.